I would leave it. You could color it with a permanent marker if you like. I have to tell you (and anybody else that reads this post) The back of my wall hangings and a lot of my table runners are not something that I get too involved with. I just refuse to use a high priced premium fabric for something that is only going to be seen by the wall. I usually choose a solid color and I'm not too concerned if the quilting shows on the backing. My friend and I went to the LQS on Friday and he found a pattern for a large wall hanging he liked. He purchased all the fabrics using the measurements from the pattern (just gave the pattern to the gal that was cutting his fabric) and once we got back to my house, he realized that the pattern called for 3 1/2" yards of backing fabric ( probably 3/4 yd will be used on the front) !! At $11/yard he got a pretty expensive backing fabric for a wallhanging!