I definitely know some fabrics pick up color more than others. When I was a new quilter and didn't know about color catchers I did a load of fabric and a red fabric bled...but only ONE other fabric in the load picked up the color! I had several light fabrics in that load (tempting fate!) but only a pale blue fabric picked up the red; the other fabrics didn't show any bleed at all. I never did figure out why.