Really cool article here from of all places NASA (go figure) courtesy of the Signal Vs. Noise blog. Entitled "DESIGNING A COLOR GRAPHICS PAGE", it really breaks down a process of utilizing color to maximize user understanding of information.
Color for its own sake is better kept to the domain of art. Functional design, like that of software user interfaces, need to be much better thought out, reaching for both utility and aesthetic qualities. Not an easy goal to achieve. The NASA article is a very good, if erudite, treatment of the subject.
UI wonks and wonkettes always mention Jakob Nielsen. Myself, I have never been a big fan of his. Sorry, I know all user interface snobs are supposed to be, but Nielsen's own website has famously ugly design and (gasp) poor usability. I am not making this up! Plus his big famous book was really boring.
I am much more a fan of Steve Krug and his fantastic "Don't Make Me Think". Now THAT is a book on usability. It probably took a really long time to write such a short book.