I was also thinking French Braid, however, for your idea of the slow change in colors, I don't think you can beat the Flowering 9 Patch... or in your case, I think you could call it the Flowing 9 Patch! I see no reason you couldn't start it in one quarter of the quilt and work out from there with the design rather than from the center working out to all edges equally if you wanted to. Just plan out your colors on graph paper first. You would be leaving out the floral and just going to the next color gradation as you move out. I think it can easily be done as long as you number your fabrics and your graph pattern to help keep things in order. LOL Now you have me wanting to try it, too.