Personally, I like them all, and would consider making a 9patch-like background. For instance, do one background color for all the squares in a left-top to right-bottom direction, then another for the right-top to left-bottom (the center block could be either one). Then a 3rd color along the inner V of the top and bottom, and middle of sides. The 4th color could be the middle of the top and bottom, and inner V of the sides. Does that make any sense to anyone?!? I have a very vivid image in my head, but don't think I am describing it well. Oh, well...
No matter what you decide, it is going to be a FABULOUS quilt! Great job!!!