Do you have a particular favorite color that you want to use in the quilt? Start there, pick one fabric or two that you like the most and then find fabrics that are lighter and some that are darker. I know this is not much help. Do you like near a quilt store that you can go visit and get some help? If I lived near you, I'll happily accompany you to a fabric shop and spend your money
Also, take look here at the Bargello Quilt tag for some color inspiration.
http://www.quiltingboard.com/tags/bargello+quilts.html
Ok just had another thought, you can make it all in one color just different values or you can use more than one color, as you audition the bolts, set them side by side until you find a pleasing arrangement. If you have a digital camera, take photos of the fabrics and use the BW feature, it is much easier to tell the value in a black and white photo. Hope this helps you a bit.