So you're using a numeric representation of colors (RGB) to prove to me that black is darker than red.
By doing this, you're basically proving my point.
1) different people may have different opinions on "obvious" statements
2) the simpler the statement is, the easier it is to accept or reject it
If you give me two color plates, one is black, and one is red, I might find people who disagree which one is darker.
But if you give me photo measurements, I will say that one is objectively darker with respect to a specific metric (e.g. visible photon energy flux, YCbCr luminosity, CIECAM02 luminosity).
No, I’m not doing that at all - I’m simply creating a well-defined understanding between us about which colors we are talking about, so that there won’t be any confusion. If you were sitting next to me, I could show you some other two colors in person, with no reference to RGB or to any other numeric representation, and the exact same argument would stand.
No specific metric can ever show that #FF0000, as it is displayed on any reasonably well-balanced monitor, is darker than #600000. If somebody invented such a metric, we would say that this metric is either incorrect, or misuses the word “darker”. This would also be the case if no other metrics existed before it. Therefore it is clear that our understanding that #FF0000 is darker than #600000 is independent of any formal description of darkness, and comes prior to it.
And you are still avoiding, for some reason, my main argument, which had nothing to do with colors, and dealt specifically with 2+2=4.