Somehow it seems intuitive to sort fabric by color, but now that I've been at this longer, I listened to the very good advice of Maria Elkins to sort my fabric in preparation for my next class with Nancy Crow by value. I'm taking 4 "under the bed" style boxes, so Saturday I sorted by 4 value ranges (very light, medium-light, medium-dark, dark). As Maria points out, in a box full of lights, it isn't hard to spot a particular color.
This didn't take very long because I had a cardboard value finder. I may go back later and set my camera to black-and-white mode in order to spot some of the borderline cases so that I can refine my sort.
I'm taking a photography for textiles class soon and this photo is a good reason why. My darks came out looking like medium darks (on the left) and they really are much deeper colors than that. This flash photo really bleached the darks out considerably. I'm looking forward to getting better at this!