FWIW, I have a fat quarter of fabric I bought at a quilt show. It was a beautiful dusty lavender, I had to have it, even though it was hand dyed. I must have washed it dozens of times over the years in futile hopes of success. It has long since lost its original color and the thing still bleeds. I've given up trying to wash it anymore and we have developed a love hate relationship, I glare at it, and it sits on the shelf and grins back at me.

I have noticed that just because color washes out of one fabric does not mean it will adhere to another fabric. Thus the reason color catchers work. Also, I believe fabric has to be treated to accept dyes, when you are buying fabric to dye it has aa special chemical added to it. (PFD = Prepared for dyeing). So before I would throw out a large amount of fabric I wold wash it with something to see what happens.