Color catchers are great but they do not stop heavily dyed fabrics from bleeding over and over again. I have always used vinegar to set the dyes but I do know there is a product on the market that does the same thing. I like the vinegar because then I know what is on my fabric. (allergies here) I do not know the chemicals that are in the other product. (sorry the name of it escapes me, but I believe someone here knows the name)
I hope this helps.