Recommended Book

Color: Messages and Meanings by Leatrice Eiseman, is old news, but I still need to put a plug in for it because it's good reading and oh, so helpful with color combinations. I refer to it often.
The first part of the book talks about color and messages it can convey, next it shows color combinations and talks about different moods. In the back of the book there are even PMS conversions to CMYK, which is very helpful if you don't have a Pantone booklet at your disposal.