Liking #21 and #8 like the idea a lot, not the specific execution. Looks like an exploded diagram…like the parts are coming apart, not together. There should be a real sense of them fitting together, two parts creating a whole. Intertwined even. More like a puzzle cube in a way. Not wild about orange. I would choose a non-complementary color to go with the blue, like green or purple.
I had started to move away from #8 because it wouldn't work in black and white. However, I will revisit and see if I can't improve. Thanks for the feedback... Andy