Steve Schoger has a book coming out called Refactoring UI and it looks like it’s going to be awesome. He just released a teaser for building a color palette. I’ve read quite a bit about color palettes, and while I’m not a designer, I have taken some design courses and I did win 2nd place in design competition for a Led Zeppelin collage (humble brag).
Also, if you are interested in UI design and have not seem the Refactoring UI videos , stop everything and go watch them.