I think tea-dying would bring the middle section closer to the colors of the bottom section. I just had the same problem with a string quilt - the white muslin I'd used looked too stark against the mainly browns/blues/reds/golds of the strings. I ended up tea-dying it and now it's much better. Had no clue how to tea-dye, so I just winged it. 10 Liptons tea bags, half of a very large stock pot of water boiled until dark brown. Then I turned off the burner, added my 25 squares and just let them sit for a couple of hours.