I still don’t know.
The background on this one is grey. I do need to buy some more grey fabric, I’m running quite low.
For this one, I think the background will be natural and the 4th color will be white. I’m not keen on making an entire quilt with a white background, and I like the idea of the white ‘popping’. I could pick up a few white-on-white fabrics or some natural-on-white designs to give the white a little variation.