
Color wheels are wrong? How color vision actually works - tobyjsullivan
http://blog.asmartbear.com/color-wheels.html
======
idspispopd
Wow, just wow.

This is what happens when someone who knows a little bit about how the eyes
and brain interpret colour decides to write an article where they fill their
gaps of knowledge with mistakes instead of doing some research. Since the
author wanted to talk about the eye, they should have kept to additive colour
only and not tried to be confusing by introducing subtractive colour, which
they neither understand or present factually.

~~~
idspispopd
Here's a few of the factual errors:

>They’ll launch into a treatise about how the Three Primary Colors

They'll try to teach you Subtractive colour theory. Artists don't actually
work in three primaries, however the idea of 3 primaries form the basis of
subtractive colour theory. An artists knows you simply don't get brighter
colours out of darker ones.

>Primary Colors produces the Secondary Colors (orange, green, and purple):

The colours shown here are additive colour mixes, not subtractive. E.g.
Magenta is not Purple. Purple has a single wavelength, magenta does not.

>infamous color wheel you probably learned in school

It's based on Goethe's colour wheel, it's artistic not scientific. (As limited
by the few amounts of colours available in earlier times.) Although it's still
a decent representation of colour than the result this author produced.

>Doesn't stand up to scrutiny/ Three colors of ink which, when combined,
produce all others: cyan, magenta, and yellow. (Black is included as a money-
saver — black is the cheapest and most common color; it’s cheaper to have a
black cartridge than to dump ink from the other three.)

CMYK does not produce a full gamut of colour, not anywhere near it. Black is
not included as a money saver, but because CMY simply doesn't produce a decent
'black' and there can be registration issues. What CMYK does produce is a nice
compromise of commonly occurring colours, however you won't get a vivid blue,
green or red out of it - there is simply no building blocks in those colours
to produce a good version of each. Instead you'll get a purplish blue, a
yellowy green and an orangey red. This is why printers have 'spot colours'.

>But wait! I thought the “Primary” colors were red, blue, and yellow, not cyan
(bluish-green), magenta (bluish-red), and yellow.

Not only does the diagram falsely misrepresent the results of mixing of CMY
colours(e.g. it should be a dark mess in the centre), but it also falsely
represents the individual colours themselves. It's actually pretty difficult
to get a computer screen to display a true Cyan, which is not, in any stretch
of the imagination "bluish-green".

At this stage the author has created a bunch of confusion, seemingly his own
because he doesn't truly understand what is going on here. The actual
difference between additive and subtractive colour aren't explored or
explained. There are lots of common school boy mistakes like assuming
subtractive mixing produces similar colours to additive mixing, e.g. he shows
that purple is akin to magenta(it's not), or that you can get any colour your
want out of mixing three primaries(you can't). Or that RGB, or CMY allows for
a full gamut (neither do.)

>This isn’t adding up. Let’s turn to science. From here the article gets
better, but it trips a few times before getting to actual physiology.

For a short while he talks about the 'magenta' problem, which actually is well
resolved. It's called an extra-spectral colour, it's not generated via a
single wavelength, but rather the absence of wavelengths from white light.
Oddly later he mentions this.

>Opposites

"Complements" rather, are well resolved scientifically, there are two sets of
complements and two colour wheels to demo these. Since he's talking about
eyes, he should just focus on additive colour.

The wheel the author has created is utter rubbish, it skips swaths of
wavelengths and is only interested in preserving 'opposites', which are
represented by incorrect renditions of those colours anyway.

~~~
barrkel
In a way I appreciate your pedantry (though not your tone), but I must also
say that the details you add seem to be technical, specific to printing and
not particularly important to the point of the post.

~~~
idspispopd
Half the article is about subtractive colour, which happens to be
print/painting/any kind of colour mixing which isn't combining light sources.

The author (is it you?) has done zero research on the topics they don't
understand, and deserves any amount of critical writing in response.

The whole point of the internet is that it represented the end of people
waffling bullshit, access to accurate information is there, and if people want
to run around spreading incorrect information they deserve to be taken down as
many notches as possible.

I might also add that this is important to the authors conclusion, should the
author has done any real research they'd see that not only does a colour wheel
that addresses their concern exist, but that they've misrepresented the
foundation of their entire argument to begin with.

~~~
leephillips
But every one of his illustrations has a "pin" button on it. And that's really
the point, isn't it?

------
sp332
In the S/M/L chart (this one [http://asmartbear.wpengine.netdna-cdn.com/wp-
content/uploads...](http://asmartbear.wpengine.netdna-cdn.com/wp-
content/uploads/Cone-fundamentals-with-srgb-spectrum.png)) you can see that at
the right-hand side, the M (green) activation is pretty low and goes to zero
where L (red) is still strong enough to be visible. But there's no frequency
on that graph where M (green) is active all by itself. So you've probably
never in your whole life experienced a pure "green" sense input!

CIE takes this into account when defining visible color spaces. Since you have
3 "primaries" you would expect the colorspace to be bounded by a triangle,
each corner being a pure input of each primary. But you can see here
[https://en.wikipedia.org/wiki/International_Commission_on_Il...](https://en.wikipedia.org/wiki/International_Commission_on_Illumination)
that the top green corner is missing. That's because there are no frequencies
of light that would let you see any color that is "greener" or further toward
where that corner would be.

OK one last thing before I get to my proposal :) Your eyes gradually adapt
_against_ the colors you are looking at. For example if you're wearing
red/blue 3d glasses for a while, when you take them off things will look
greenish out of the "red" eye and yellower out of the "blue" eye. You can play
tricks like this
[http://wxerfm.com/blogs/post/jfrieders/2012/jan/25/picture-c...](http://wxerfm.com/blogs/post/jfrieders/2012/jan/25/picture-
cool-optical-illusion-star-negative-photo-/) In fact it's possible to exhaust
some of your photoreceptors, like the "spot" from a camera flash or the streak
from a glare of sunlight.

So here's my idea: if you strobe a really bright red & blue light, enough to
temporarily blind the S & L receptors in your eyes, you should be able to see
a green that is more pure and intense than you have ever experienced, right
off the CIE chart of visible colors! Who's up for experimenting? :)

~~~
hammock
>But there's no frequency on that graph where M (green) is active all by
itself. So you've probably never in your whole life experienced a pure "green"
sense input!

I wonder if there is a medical condition out there where someone is missing
the L (red) cones in their eyes - in that case they COULD see pure green sense
input. In fact despite being disabled, they could see colors that everyone
else is unable to see!

edit: It does seem to exist, protanopes (a severe form of red-green
colorblind) are missing the red cones. So if I understand correctly, while we
tend to think of them as having a restricted spectrum, they may actually see
some colors that others can't.

~~~
colanderman
No, they wouldn't be able to see colors most people can't -- they'd be able to
_experience_ colors most people can't. It's an important difference. Their
"ultra-green" would really correspond to our "yellow".

~~~
hammock
Thanks for clarifying. That's exactly what I meant.

------
derekp7
He's got one minor thing wrong -- in CMYK, black isn't there to save money, it
is because that in theory, CMY mixed will produce black, but in reality the
ink's aren't "pure" enough, so they end up being a muddy color. So the K is
there to produce the darker blacks.

Also, a) Ink is translucent; light goes through the ink, reflects off the
white paper, goes back through, and that affects the color change of the
light. Therefore ink uses CMYK. Pigments in paint are opaque, so light
reflects directly off them. In this mode, Red-Yellow-Blue-Black works. For
monitors, light is emitted not reflected at all, so that is why they use RGB.
Oh, and many colors can translate from one model to another, but not all of
them. Some can only be expressed in RGB but not CMYK, others can only be made
in RYB.

~~~
praptak
True, and not even the K in CMYK is 100% black, hence the notion of "rich
black", which is a collective name for colors produced when K is at maximum
and yet other colors are added to the mix. It even has its own Wikipedia page:
<http://en.wikipedia.org/wiki/Rich_black>

------
strebler
It's definitely an interesting topic and a nice high level overview of the
problems of colour and colour spaces. I like the 4 point colour wheel in some
way, but I don't entirely see the benefits.

From a computer vision perspective, this representation still has problems (as
do all colour spaces). Look at how massive the green space is. There's 4-5
greenish slices that are close to each other, yet only 1 slice for yellow and
2ish for red. Red is the colour humans see "best", physiologically it should
have the largest representation, whereas blue should be smallest.

From the simpler side (i.e. a basic colour wheel application), I'm not sure if
this makes it much easier or faster for me to find a colour.

In any case, the article is very nice high level overview of a fascinating
problem.

~~~
AceJohnny2
"look at how massive the green space is..."

This is why, in non-symmetric color coding systems, Green is given the largest
share. For example 16-bit image formats give 5 bits for Red and Blue, but 6
bits for Green. The Bayer color pattern pattern used on CMOS sensors
(basically all sensors on consumer devices) has interleaved rows of Green and
Red and rows of Blue and Green: twice as much green as the other colors!
Finally, green represents more than 50% of Luminance!

From an evolutionary perspective, it makes sense to be more sensitive in the
green spectrum: we were surrounded by green plants. Better catch the nuances
to better identify predators or prey!

------
commieneko
I knew when I saw the title I was in trouble. I've got stuff to do tonight,
and don't have time to write a real response. And a _real_ response isn't even
really necessary; there's nothing wrong with the all the various color
theories and models that paper the floor of the world. They are all imperfect,
but often useful, approximations generally designed by trial and error usually
for specific use cases.

So the notion that those wacky, touchy feely artists (aren't they cute!) don't
know jack about color is specious. Their knowledge is specific to their domain
and tools they use. While many of them could use some touch up here and there,
it's really not necessary because ... dramatic pause ...

 __ _It doesn't matter!_ __

No artist is trying to produce a particular color found in nature. They are
trying to produce the _appearance_ of a perceived color of a certain local
color source under certain lighting conditions, and, here's the kicker, under
certain psychological conditions. A good artist can make you think you see any
color they want to using nearly any available palette. The more colors the
better, up to a point; limited palettes can be a very powerful tool.

And the color interactions you get when mixing pigment paint is not just an
optical problem, it's a chemical problems as well. Artists do some very odd
things to get the colors they need. I'm reminded of a story about the MIT
hackers back in the 50s/60s who found out that a radio produced interesting
sounds depending on what the computer next to it was doing. The electronics
would produce radio noise that would be played as sound. With a little
experimentation the hackers found out what kind of operations produced what
kinds of noises, and at what frequencies. So they wrote one of the first
computer music programs using this system. Needless to say, they needed to
make the computers do some pretty odd and complicated things to get the radio
"noise" they needed.

The chemicals we use for pigments are the ones that "happen" to reflect, re-
emit, or transmit light at particular frequencies. Finding the colors is hard
enough, but you also have to worry about how they interact chemically with
each other, for both stability (boom!) light fastness, or toxicity. In the
early days, toxicity wasn't too big a considerations, and many, many artists
died from rather nasty chemical poisoning.

If you are interested, get a book on oil painting. _Creative Illustration_ by
Andrew Loomis is a pretty good place to start. I also highly recommend John
Gurney's books on painting or artistic color usage. These are good things to
read even if you have no intention of every picking up a brush, because they
are not at all about the physics of color. They are about using color to
communicate and create a certain kind of perceptual experience. If optics and
physics were what was needed to understand the mechanics of picture and image
making, anyone with a good camera could do the job. But a good photographer
knows that their job is _not_ to perfectly transcribe whatever may be
happening in front their lens at any old arbitrary time. (As an alternative,
you _can_ learn a lot about practical color theory by studying older
photography books.)

As for CMYK and RGB color spaces, these are simple but quite effective tools
for dealing with color in a purely mechanical way. And they dovetail rather
nicely with the artistic color models used in the past by painters and
photographers. It _is_ important to know that these are abstract color models
intended to produce an approximation that is almost always good enough for
most everyday usage by non-specialists. Specialists use tools that are often
similar, but with more special cases and provisions for calibration and feed
back situations.

If you really need a color model more closely tied to how human visual
physiology works, LAB was designed as a good approximation of that.
Specialists sometimes use other, often proprietary systems. If you need this
level of knowledge, you got some book _larnin'_ to do. No blog posts or
comments on HN is going to help you too much.

Finally, speaking of human physiology, the model of filters he describes seems
to make it impossible to distinguish red from green. In other words it seems
to be describing a system that exhibits red/green color blindness. I have a
suspicion that the author read a complicated article, got hung up on the part
that talked about r/g color blindness, and thought that was the general case.
When I've talked to specialists about this kind of thing, the answers I get
are all the equivalent to "It's complicated ..." Human visual physiology is
real complicated, even the purely mechanical aspects of it, and frankly not a
lot is known about some aspects of it. What I've been told is that when you
reduce the complicated aspects of what _is_ known into a workable set of
approximations, for specific use cases, you get something very similar to ...
wait for it ...

 __ _Artistic color wheels and paint mixing systems._ __

~~~
jacobolus
I agree that this blog post takes a sort of silly tone, and also that many
artists are very sophisticated in their understanding and use of color.

He goes wrong in a few places, for instance in using quite confusing
coloration of his diagrams, and he really shouldn’t put the labels R, G, B on
cone responses: these are too evocative and are likely to confuse as much as
they enlighten.

But to be fair, basic paint mixing models in artists’ heads often aren’t very
good, and many artists would really benefit from studying human color vision
more seriously. Explaining how vision works to visual artists, especially
amateurs, is one of the more rewarding things I ever do: you can see these
lightbulbs going off in their heads as a bunch of stuff that they know
“intuitively” and experientially is given proper names and ordered into a
comprehensible model.

> _As for CMYK and RGB color spaces, these are simple but quite effective
> tools for dealing with color in a purely mechanical way._

I think these spaces have no place being taught to non-specialists. They are
not intuitive to humans, being based on particular technology rather than on
human vision. Any user interface which exposes these color spaces to non-
experts is letting them down. Just as bad is using HSL or HSV or some similar
trivial derivative space. Image editing software, in particular, is
dramatically harder to use than it would be if the dimensions were at all
relevant to vision.

> _If you really need a color model more closely tied to how human visual
> physiology works, LAB was designed as a good approximation of that.
> Specialists sometimes use other, often proprietary systems._

Specialists looking for models related to vision mostly use open, publicly
developed and specified models. At root, most of modern colorimetry is based
on the CIE system, which has served very well since the 1930s. Recent fairly
effective models that would be useful for software include CIECAM02 and IPT,
which behave better in some ways than CIELAB, but are a bit more
computationally expensive.

> _If you need this level of knowledge, you got some book larnin' to do. No
> blog posts or comments on HN is going to help you too much._

That’s reasonable. Let’s start with some pointers to good sources!

For this audience, Maureen Stone’s SIGGRAPH notes from 2001 are a nice first
start, with lots of pointers to other good resrouces:
[http://graphics.stanford.edu/courses/cs448b-02-spring/04cdro...](http://graphics.stanford.edu/courses/cs448b-02-spring/04cdrom.pdf)

For anyone who wants to really dive deep, I recommend
<http://www.handprint.com/LS/CVS/color.html> (edit: Actually, I see that the
blogger does link there. So that’s nice.)

Also, anyone looking for pointers to books, feel free to email me (address in
profile), and I can point you in some direction based on your specific
interests.

~~~
commieneko
Artist's color mixing models aren't simple mechanical ratios. They use
emergent properties of chemicals that just happen to be a particularly useful
color. In fact, artist try to do as _little color mixing as possible._ Mixed
pigments of the types artists use do work like the inks used in printing and
the dyes used in RGB displays. Color wheels are guides and approximations.
Learning a color theory that is more accurate is counter productive because
you can't find pigments that behave that way. And if you ever get a chance to
see a painting in the flesh and compare it to even a very good reproduction,
you will see that the simple color model primaries used in printing and on
screen reproduction are only loose approximations of the real colors.

Now what an artist _does_ need to know is how color works perceptually. And
the models used for this are pretty good. And remember the intended result is
seldom "photo realism"; not that photos are particularly realistic. But that's
another discussion altogether.

If you are talking about amateur artists, or beginners, then, sure, lecture
away, but if you talk to someone who's been successfully painting for 40
years, my advice is to listen to him/her. They may or may not know much about
the physiology of human vision, but don't be surprised if they do, but they
certainly know the ins and outs of making you _think_ you see what they want
you to see.

The nice thing about standards are there are so many of them. I've spent more
time than I cared to writing software to convert and compare between systems.
They are a few _lingua franca_ systems, but if you are doing serious, critical
color work, your special cases are going to be the bulk of your job. Which
only makes sense if you think about it. The sources I used are going to be
about 30 years out of date, and the chemistries and optical systems no longer
relevant.

Doing mechanical color reproduction is a specialty and few people need to know
more than the basic RGB/CMY model and whatever specific systems that they need
for their domain of activity. These days these models are very good and well
tuned for their domains. Unless it's a brand new technology (Or NTSC; don't
get me started!) This usually means working with a specific palette and color
gamut.

And while a lot of people in the various industries feel that they are dealing
with the _real_ color models, and the rest mere approximations, there is no
such thing. In the end it all breaks down and you are left with making
specific measurements with specific types of equipment for use with specific
use cases. And then you calibrate.

Color theory is very much a case of the map not being the territory.

~~~
jacobolus
> _Learning a color theory that is more accurate is counter productive because
> you can't find pigments that behave that way_

Learning theories can be tremendously helpful for crystalizing existing
knowledge. Ultimately the only way to learn is to make visual art and look at
it, a whole heck of a lot. But having theoretical models can help guide that
thinking and looking, and can forestall a lot of confusion.

There are two kinds of models an artist needs to learn to deal with color:

(1) How the human eye sees color. This is so that texture and shape can be
made to convey the desired effect of the picture. It’s helpful to learn about
simultaneous contrast, adaptation effects, and even more obscure things like
Ralph Evans’ (Kodak) theories about what he called “brilliance”. Learning this
doesn’t tell you how to mix the paint, but it helps you figure out what
results you should aim for.

(2) Color reproduction technology: the physical properties of paint / displays
/ printers / whatever.

Many people in the general public, including many artists, don’t properly
understand the distinction between (1) and (2), and also take the radically
oversimple concept of primary and secondary colors, etc. (whether it’s
elementary school teachers with their red, yellow, blue, or programmers with
their sRGB) as some kind of ultimate truth.

All of our models of color are approximations. Color is complex and
contingent, depending on observer, lighting, viewing conditions, temporal
effects, and so on.

~~~
commieneko
My point is not that artists shouldn't learn about color and learn color
theories. And I'm not saying that they shouldn't learn how human's see and
process information. What I'm saying is that they already do that. But they
are doing it with different models and techniques that are keyed to their
domain and tools.

Sure, learn about RGB/CMY. It doesn't hurt. And printing technology, which is
a _different domain_ is very similar, though not the same in critical areas.

There's nothing magic or even very special about the methods and models you
are talking about outside their domain of use.

If you are a designer who is working in print or onscreen display, you will
learn to think in RGB/CMY(K). But there's _nothing_ universal or special about
that system compared to other systems. It's not more _science_ compared to the
systems artists use in their various working practices.

It's _not_ more keyed to human physiology, in fact I'd argue that it is less
intuitive and useful. I'll agree that it's not a numeric model and it's not a
model designed for _accuracy_ ; and reproducibility. But it _is_ a model
tightly coupled with human perception, expression, and communication.

(As a designer working with digital imagery and renderings, I make major use
of HSB style color models. I've written many special purpose tools for giving
me effects I want, using all kinds of hair brained models, and then converting
the results into RGB.)

To create a numeric model of how artists use color would be very difficult. If
it weren't we'd be able to make cameras that made illustrations. And we can't
and don't.

What an artist does is make an observation, and I mean this in both an
abstract and practical sense. He or she then takes that observation and
creates an abstraction of it, and then tries to make a work that communicates
that abstraction. With the tools and mental model at hand.

There's a photo floating on Reddit right now of where a hair stylist has
arranged hair clippings found on the floor in the shape of a dog. It's a
wonderful piece of throwaway art. Now you could sit down and say, "If I take
these hairs and arrange them with these percentages, I'll be able to get this
range of colors and represent these textures ..."

But that's silly. The artist sees the hair, it reminds them of something, like
a dog, and they spontaneously arrange them, making corrections and following
intuition as they go.

<http://i.imgur.com/ZNmxV.jpg>

Now if you are going to start an artistic tradition of arranging hair
clippings for art, you might come up with some theories to model different
effects. But I don't think you are going to be making numeric models. For one
thing you never know what kinds of hairs you are going to find on the floor.
Instead you are going to learn to "fake" it by using the relative and
comparative artifacts of the human's visual and perceptual system. But it will
almost certainly be intuitive and spontaneous. Lots of trial and error.

If this art form becomes a tradition, then special markets will develop in
hair clippings, special dealers selling hair patches arranged nicely in
special ways, maybe even a bit like RGB/CMY. (But don't push it.) Hair dyeing
might become a specialty, but purists will insist on nature hair and natural
hair colors. There will be much arguing about it and many bar fights.

And if you decide that there's a market in selling hair floor arrangements in
mass quantities, then you might see something akin to what you see in modern
printing or broadcast. Specialists will arise.

And most artists will say, "It's hard enough to make a pile of dog hair look
like something interesting while worrying about all that. I'll make a good
pile of hair and leave it up to the specialists to mass produce it. Maybe I'll
use standard hair patches to make things easier, I do like it when the
reproduction is well done. But I hate limiting my choices and opportunities,
and besides the reproduced hair piles never look as good as the original
anyway. After all, it's just a copy."

~~~
jacobolus
I think you’re misunderstanding me, because I mostly agree with you.

> _There's nothing magic or even very special about the methods and models you
> are talking about outside their domain of use._

Learning about how cones & brains interpret light into the colors we perceive
is definitely “special” compared to models designed around some particular
physical medium like ink or dye or CRT displays, and the domain of use is “any
time you want humans to look at colors”.

> _[RGB/CMYK] is not more keyed to human physiology, in fact I'd argue that it
> is less intuitive and useful._

Sure. Which is why what I advocate teaching is the physiology and models aimed
at approximating it (something with dimensions like the Munsell system or
CIECAM02, etc.) ... which is absolutely more “intuitive” than RGB or CMYK or
some paint mixing model, in the sense that it tracks perceived color
attributes directly.

------
mbostock
If you want a good introduction to color theory, see Marc Levoy's lecture
notes from CS 248 (Introduction to Computer Graphics). The notes are quite
dense but contain a lot of good information.

[http://graphics.stanford.edu/courses/cs248-08/color/color1.h...](http://graphics.stanford.edu/courses/cs248-08/color/color1.html)

[http://graphics.stanford.edu/courses/cs248-08/color/color2.h...](http://graphics.stanford.edu/courses/cs248-08/color/color2.html)

------
adrianhoward
_Ask any artist to explain how color works, and they’ll launch into a treatise
about how the Three Primary Colors_

Nope.

If you ask an artist or designer about how colour works when you'll usually
get is a deep sigh, followed by "it's complicated", followed by a
_looooooooooong_ explanation of some of the options presented here and a good
few more besides.

(Fascinating bit of trivia: There is some moderatly persuasive evidence that
some folk have more varient cone cells and can see more colours than people
with "normal" vision. See [http://www.post-
gazette.com/stories/news/health/some-women-m...](http://www.post-
gazette.com/stories/news/health/some-women-may-see-100-million-colors-thanks-
to-their-genes-450179/) and
<http://www.klab.caltech.edu/cns186/papers/Jameson01.pdf>).

It's usually developers who have the broken models of colour perception
because, unsurprisingly, they're not trained in it :-) Artists and designers
deal with multiple colour models all of the time - just go look at how many of
the preferences in things like Photoshop are about managing colour... and
that's just in the digital editing space.

------
teilo
I'm somewhat surprised that no mention was made of L * a * b color, since the
four point color wheel corresponds to the a and b channels.

------
ken
> Every seven-year-old kid in America is taught that “the opposite of red is
> green” and “the opposite of blue is yellow.”

Did I sleep through second grade or something? I've spent the first 30+ years
of my life in America and I've never heard of this.

~~~
evincarofautumn
Different schools teach different things; many don’t introduce colour theory
at all. And it’s an odd thing, but most people don’t know intuitively how
colours combine or invert. Of course, as a synesthete and maybe a
tetrachromat, I’m not really statistically relevant to this discussion. ;)

------
arundelo
Terminology note: This is called the opponent process theory.

<http://en.wikipedia.org/wiki/Opponent_process>

------
idan
I had a short bit about this in my datavis talk at Pycon. Youtube link
directly to the explanation of vision / color physiology:
<http://youtu.be/vfYul2E56fo?t=18m31s>.

------
nsns
Nice article, even better comments. But am I the only one who thinks
explaining stuff by "it's because your brain tells you that..." doesn't really
solve anything, simply relocates the mystery?

------
duopixel
Previous discussion (more than a year ago)
<http://news.ycombinator.com/item?id=2166494>

------
SonicSoul
awesome post. this is not 100% related, but if you're interested in color as
it pertains to human perception (and how to cure color blindess and how a
mantis shrimp can perceive 6x more color) there is a great podcast on
RadioLab! <http://www.radiolab.org/2012/may/21/>

------
gcb
could be a much better article if not so sensationalist about kindergarten
learning not being perfect.

