if not a solid black, you could try a charcoal gray. good luck.

IMHO cornerstones would make it look like an Irisih Chain design gone wrong. I like the solid black sashing advice but I'd also try auditioning a wide solid dark green and using the solid black for a border.

Take your blocks to the store and audition colors. There have been lots of nice suggestions posted. I can't wait to see what you choose. I certainly love it so far!!

Cleodaisy

I am thinking a deep forest green.

What I did when I had that problem was take pictures of several of my blocks straight on, so that they look as square as possible in the picture, and then I tested different colors by "pasting" rows of them in Windows Paint (which is usually included on every Microsoft computer). Then the background color can be changed, and you can see for yourself what the effect might be. Here are some examples of one. The blocks don't look as square as they are, but it doesn't really matter for this purpose. I tried several others, but wound up choosing a light green. Haven't sewn it yet.

WOW! Beautiful blocks. I don't normally like green, but your blocks are awesome. I think I would go for black as it would make the blocks really pop. Even the ones with a lot of black in it would pop if you used a solid black. JMO

I agree with most everybody else = black! 'twould surely make those gorgeous blocks pop!!

I agree---Black.

Perhaps I am not seeing the colors correctly. But my first thought was navy blue.

Daring to be different here. My first thought is purple! A nice violet shade would be unexpected and would allow those blocks sing as individuals. Black sashing could work but I think it would muddy the precision of your pretty blocks. Just a thought.......out of the box.