I never prewash EXCEPT for REDS! and with them I only just put a small sample about 8x8 in a hot water bath in clear jar to see if the color bleeds SO in your case I would find a Scrap of your Quilt fabric and do this test BEFORE you wash this Quilt!! And IF it makes the water turn red or pink you should try the Color catchers maybe 2 or more if your quilts big.
