I use a product called "color catchers". You would be simply amazed how well they work. The "sheet" of color catcher that is in the washer would look like your purple towel above and everything else - including white - would have no fading on it at all! I do no pre-wash. I use the color catcher when the quilt needs washing. When given as a gift - I include a box of color catchers with the quilt.