I would think it would be better to dry it in a dryer so it isn't wet as long. Wouldn't being wet cause the purple to migrate over to the light fabric? I always throw my quilts into the dryer. It also gives them that vintage puff look.
I have never used color catchers, but I usually test little snips of all the fabrics I am going to use by first soaking them in HOT water, them putting the snips on wet, white muslin. Then I put another piece of muslin on top and let it all dry. Then I pull it apart to see if any dye has transfered to the white muslin. If so, that color goes away. Then I don't have to worry about any bleeding in the wash.