I checked my purple batik I mentioned earlier. Had been planning the colors to use with it - and had folded up one of the light blues with the purple batik and put it on the shelf. Guess what! When I unfolded it yesterday, there was purple dye all over the light blue - just from folding them together.
I'm cutting my losses now, and throwing that one away. Don't remember which store I bought it from (after Oct last year), so can't warn you about that particular fabric. I really really appreciate this thread! Since I hand quilt, I'm thinking I want to buy only guaranteed colorfast fabric.