Retayne and a color catcher in the wash. but sometimes you do get one that just wont quit, best use if that is the case...wall hanging that won't get washed :(
if it is going to stop
retayne will do the trick (or synthropol which is what we use to wash away any 'loose-colors' when we dye our own fabrics. it only takes about a teaspoon in a washer, but it works.
good luck; good thing you tested!