My first thought was that I wouldn't add any colors -- there are already almost too many. I'd go with a 4-4.5" wide white sashing to add some unity. Then, for quilting, I'd either go with matching thread colors for each block, or a very light, light blue across the entire top -- could even use a blue variegated like Aurifil #3770
However, since you mentioned a Fall color scheme, the other option I'd consider would be to use that yellow-orange from the center block with the darker blue background for the sashing & then would quilt in black. Would definitely read as autumnal/Halloween-ish.
Here's an idea of what I was thinking:
[ATTACH=CONFIG]554616[/ATTACH] [ATTACH=CONFIG]554615[/ATTACH]
Apologies -- my Adobe Suite isn't working properly so I tried to re-color in Paint & it didn't work out so great. Just imagine in the 2nd one that everywhere you see light blue "stitching", it's black instead.
