Yes they may vary. I'm not sure which brands are more prone than others, but I have ran into it. Recently my small quilt group decided to do a challenge where we picked 1 focal fabric and the same pattern that we all had to use and then we were free to pick all our other fabrics. The fabric we ended up choosing was a floral print from JoAnn's. One of the gals and myself made a trip to the neighboring towns to buy the floral for everyone and we noticed a big big difference. One bolt we refused to buy as it was so faded looking and the others were vibrant. If you looked closely we could see a difference in each bolt. Normally I don't buy large amounts of one fabric so it isn't a problem.