Your rainbow quilt looks super Murphy! I just picked another m. of my black for borders on my top. I am still working on my blocks but wanted to get the black off the same bolt of fabric before it was all gone. I found a great 100% black cotton at a little Mennonite store that was 90 inches wide and only $7. 95 a m. I am aiming at a close to 90X90 square quilt so I have a loooong way to go.