I generally don't pre-wash. I have never had color bleed but I use color catchers when I wash my finished quilt. I use inexpensive muslin for foundation to do crazy quilt piecing and strip piecing and I do wash that because it is a loosely woven fabric because it is so cheap and I know the shrinkage will be more than the other fabrics. Some quilters react in horror when they find out I don't pre-wash. I think it is a personal decision and there really isn't a right or wrong way.