90% of the time, I draw my color ranges directly from source material with a color-picker tool before starting. Sometimes I paint directly with those, other times I end up using one of the many templates I've set up along the way for repetitive elements, using cont/hue/sat filters and then cleaning up with burn/dodge/smudge.

The difference is that you're setting out to make skins that look like game sprites, and I'm not. I prefer the smooth shadowed, subtle highlights look.