I, too, used to have this problem. I'd audition fabrics for quilts and question how it would look.
To make things easier, I purchased Electric Quilt which has been worth every cent as I can design a quilt, then make changes in the overall coloring until I'm happy with it. I don't have the actual fabrics to show, but similar fabrics or colors give you a much closer idea as to how the finished product will look.
Try something similar and most of your choices will be a lot easier.