Neesie

Sorry! My "neutral" is probably the same as your "natural." I think of "neutral" as either natural or gray, depending upon what blends better. What I meant, though, is you could treat the red/blue borders as one; instead of thinking of them as two separate colors. Hmmmmm. I just re-read your original post and might be saying the same thing you were already planning to do. In other words, you'd be outlining the white/off-white, rather than the colors.

Depending on how much you just want to "just get it finished," you could also just cross-hatch quilt the blocks. Seriously, it's gonna be beautiful, however you decide to quilt it!