If this is for a graduation quilt, I have made them using the school colors. Having made some hard-used baby quilts, I'd probably not use flannel as the fluff tends to disappear or doesn't fluff any more. Too, flannel tends to fray so seams may come apart if it isn't tenderly cared for, If this quilt will be laundered repeatedly, you might consider how it will look as the colors fade with life as the quilt will know it. I've made some using black and, with use, they look pretty dull. Speaking from experience here.