I've never pre washed anything, and I use a lot of batiks. I've even used white solid cotton with bright pink and red batiks in the same quilt and never had a problem. If a quilt does have a lot of lights in with dark colours, I do throw a colour catcher in (if I remember), just to err on the side of caution.
I wash all my quilts and quilted items once they are finished to make sure they don't run/fall apart/shrink etc before they are gifted/sold.