I felt the gray wasn't working on that one. By enhancing saturation points, I mean... when going from dark to light, (and probably pretty desaturated), or just from one form to another, having a 50% blend is a bit boring. By adding some saturation you can say, hey, this thing has some color dimension too. I don't really mean saturated terminators (on a an overexposed red planet you'd only see black where shadowed, white where lit, and say, martian red on the terminator because it's the only place where you can fit in a normally saturated color. I'm more talking about sort of whimsical points of light, chromatic aberration perhaps. Actual color, perhaps. Subsurface scattering, perhaps. Self illumination, perhaps. It doesn't matter so much. It's just to bring in more color dimensionality.
I never uploaded this one for some reason.
Basically I'm talking about a more subtle version of painting with correct values but garbled colors.
A related discussion is what I'd call... color textures... color fields which consists of many colors upon closer inspection, i.e. dithering in pixel art, but with the intent of creating something more than a color rather than just a new value. The impressionists and pointillists did it with gusto.
http://en.wikipedia.org/wiki/File:Henri_de_Toulouse-Lautrec_056.jpg It's pretty common to see artists from any time mix in blue textures into warmer colors but digital art tends to be cleaner nowadays. Paul Bonner works traditionally and likes to use a copper teal:
http://www.amazon.co.uk/Out-Forests-The-Paul-Bonner/dp/1845767055 - It's sometimes a plain flat hue shift but I think the double (or triple) color texture has a different feel to it so I wouldn't call that a hue shift. It's visible on the brushstroke level.
Needless to say, this kinda stuff is difficult to do in pixel art with a small palette and so few pixels to work with. Can't quite do the dither-color thing on a tiny NES sprite (pixels are too big) and you wouldn't want to waste a color on just a saturated dot. Can play with adjacencies though, maybe colored outlines.
