Thanks everyone, this particular fabric is all pale shades, with even some white. I think I'll pass on this one & see what happens. I don't think it will be a problem if I don't prewash any including the backing,it will all be treated the same. I just needed some encouragement.
However, after what you said Mamagus I think I will prewash another kit I have which has some reds in it. Those may run and it's from Connecting Threads also.