what a fun quilt idea. Another idea for black, white and gray. It's just a jelly roll race quilt with colorful appliquéd flowers. Would be very easy to do and make an adult sized throw. Adding this to my list!
Do a large disappearing 9 patch corners made from sets of 3 fabric colors; center square - a solid color, the other 4 squares white (or the same color for each block). Play with if you need to rotate your 3 color blocks.