I'm not a pre-washer. I boldly make quilts with dark purple batiks and light pink/white batiks. Before I wash though, I soak my quilts in water with a quarter cup of salt, hand agitate, drain, rinse, repeat until there is no longer any colour in the water. Then cold water gentle cycle with a handful of colour catchers. This may not be quilt sanctioned, but it has worked well for me on that purple batik quilt as well as a dark green with creams and whites.