When I first started quilting, I was also having difficulty. I had no "artistic" bone in my body, so I always questioned and second guessed myself. One day, I thought "what the heck" and just started choosing colors that I liked, and it was pretty darned good, so I say trust your instincts, and choose what you like. Who says every quilt has to be color coordinated? I make quilts in colors that I like, and so far, the finished product is always better than I imagined when I started. Sometimes, the fabric even "talks" to me, and tells me what pattern to use with the fabric I have chosen.
On the other hand, Jinny Beyer has wonderful quilt kits available, and she also shows her quilts in different colorways for comparison. Even if you don't buy anything from her site, go to the website (jinnybeyer.com) Quilt Kits tab, and click on some of the patterns to see the difference the color makes to the final product. I will tell you, I don't buy often from her site, because I think it is a little pricey, but the ideas are fabulous.