Wah, you guys are twisting my arms like crazy!
Anyhow, have you noticed the SATURATION slider next to the color wheel? If you hold down [ctrl] you can fine tune like with any dial, by the way!
However, I will soon add more color picker options. The thing that concerns me, though, is that I don't understand why you want this kind of "accuracy" in relation to "what"? If you thought about it more in traditional ways, you would and could mix and pick colors on the fly. For example, you want it a bit warmer, you put a bit of red down, blend it and either pick the color or just work with the blending itself.
The other thing I've done as a really fascinating test was to use the brush images, make images in the colors of the light I want and in the colors of the ambient I want and then you can pick the color of what ever surface you like and switch out images based on whether you want to paint towards the light or the shadow and so on. It works phenomenally well. So well so that I want to actually add a feature for that purpose, too.
Anyway, I just sometimes worry that you are striving for some sort of perfection that only holds you back a little, you know.
There's one other thing I wanted to hook up right away, but haven't done it, yet. I want the color swatches to have different modes, which would turn them into gradients from one swatch to the next. This way you could easily create your custom color picker on the fly.
But, enough hijacking your beautiful gallery thread! I want to see much more of your art instead!