The beauty of a scrappy quilt is that the sashings don't have to match. The first thing that came to mind is checkerboard sashing, using a red fabric around the blocks that have dark fabric and then dark fabric - black/navy,brown - around the red/pink blocks. Something like this:
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Looking at your blocks, by switching the last 2 blocks on the first row, the red/pink blocks will alternate and this type of sashing would work.
I would also add a border so that the outside blocks have the double sashing too.