How did color pickers like this become so popular in non-pro situations? They are completely impossible to use for mere mortals (for example, try and pick the same color twice).
i'm sure other people have mentioned but it doesn't work in IE9 or below. You should at the very lease support IE9. If you wanna throw away IE8 or below, it would make sense to just use canvas rather than a base64-encoded image.
The gradients are defined using CSS. I think it might work if someone threw suitable declarations there. I recall IE<9 implement some custom syntax that might work.
I glanced at the code quickly and noticed `addEventListener` without `attachEvent` fallback. So that will fail in at least IE8 and below. Not sure about other things, but I'm guessing you never tried it in IE8?
I like that you decided to use some base64-packed images instead of using anything external; good idea.
You may want to include something about what browsers are supported. As it is, the page is completely broken and not usable with IE9 (1).
Nice work, though!
[1] - http://i.imgur.com/d7JFq.png