To form shadows I use the color that is a little bit darker color gamma than the base color.

character concept art



character concept art

Refining the hand:

character concept art



character concept art

Put the face color. Don't waste your time cracking the skin tone, especially
   
the face, because it is very complicates. But the standard face tone is somewhere between yellow and orange.

character concept art



character concept art



character concept art



character concept art



character concept art