Who is it for, if its for you what are favorite colors or color combinations. Are you using your stash or are you buying new fabric. If you are using your stash, pick out your favorites and see what jumps out at you. If you are buying new fabric, take a trip to your favorite fabric place and feel it calling you. I believe that fabric calls to you and you will find something you like and the backing color will come also. My stash was from a trip around the country that i took, and I stopped at every city I stayed in and bought a 1/2 yard. I sometimes asked the person cutting which is their favorite or what reminds them of where they live and now I have all kinds of fabrics from chickens to Elvis to native american and it made a beautiful peek a boo quilt that has every know color known to man and my husband loves it. The peek a boo quilt looks a lot like cathedral and its made with circles. The opposite side is multicolored. Anyway let your heart lead you.
Jane