I don't pre wash fabrics. I use several color catchers each time I wash a new quilt, in case -- and most of the time there IS extra dye, which is caught by the color catchers. I don't dry a quilt until I've looked it over carefully to make sure that all is good and no spots. Have never had a problem. Someday that may change, but I've been quilting for nearly 40 years and before color catchers I'd throw in an old white t shirt or something else that's cotton, and that worked the same way.