They are Dresden plates. The fabrics look like the Fifties or Sixties-- the browns, the foulards, the coin dots, the kooky fabric that looks like a buzz saw blade.
I like your idea of solid--maybe applique them on traditional white or white-on-white fabric, and applique some bright yellow circles for the centers?
There's a lot of blues, and they look solid. I bet you can find a nice solid Kona that will look good as sashing. If you want an updated look, pale blue or spa blue and brown is a trendy combination. If you want it wildly modern, go brighter, like black and yellow, or lime and cobalt. just play with colors nd see what you like best.
Please let us see when you finish.