I started quilting over 30 years ago, and have prewashed about once. I found that I didn't like the 'feel' of the fabric and I was less accurate with a washed fabric. I have not even prewashed reds, blacks, or any dark colors. I have never had anything run. I guess that is because I wash the quilts in cold water and usually hang to dry. I continue merrily on my way. I enjoy discussions on to prewash or not to prewash. I consider a quilt a 'fine fabric.' I treat it as I would a silk blouse--carefully but understanding that it is a fabric and meant to be washed when it is necessary. Just my .02 cents today...