When I first started quilting I bought Color from the Heart by Gai Perry. The book has a series of exercises that help you learn about color. I did the first exercise and learned from it, but didn't do the remainder. I did feel that I learned from them, however, just by reading. Actually the best advice is to practice, and decide what you like. By making color decisions on your own you'll eventually find that you are noticing colors more everywhere you look, and that is a joyful thing.