I try to buy my backing when I buy my fabric to match the one I like best However I am bad about buying fabrics I like and have no idea what I am going to do with it. Then I try to find something that looks like it was made to go with it. I have always been lucky to find something. I have only used solids once in a baby quilt. I have made two tops with scraps from the main top and loved the way it turned out. On that one I had to find solids that matched colors in the prints for the one I used for the back.