When I was new to quilting I would go to the LQS and choose a fabric that I liked and they would help my build the rest of the quilt. Most of them are really good at picking colors. Or I would go and say I want to make this quilt in a certain color way and they would help me. Now I mostly pick myself but usually have someone in the shop look at them before I buy to see if they think they work together. Just play with all the colors. Sometimes strange color combinations work.