Regarding point #2, I've found it usually balances it a bit more and while keeping the same values, makes it more colorful. If working with a limited palette, a neutral grey can be used dually with warm or cool colors on the object to cast an opposite cool/warm shadow - which usually looks quite complementary, although I can't recall seeing a warm shadow cast from a cool-colored object very often - seems unnatural as shadows are generally cooler.
http://androidarts.com/art_tut.htm - this link touches a bit on color theory from a digital-painting standpoint, though it's pretty applicable. Color and Light for the Realist Painter by James Gurney is also a good book that has some info about creating unified palettes.
http://androidarts.com/art_tut.htm - this link touches a bit on color theory from a digital-painting standpoint, though it's pretty applicable. Color and Light for the Realist Painter by James Gurney is also a good book that has some info about creating unified palettes.