I have finished clue 3!!! I could hardly believe that after counting about a thousand times while working on this clue, that I still ended up one set short. But they are all done now (including the extras), and I've moved on to constructing the A block.
Now that I am focused on the block, I'm appreciating again the cleverness of the design, and how fortunate I am that the light blue doesn't play a more crucial design role, because mine are barely visible against my neutral. I don't know what I was thinking when I supposedly checked the contrast. I think I get an idea in my head, and then stick with it regardless of the evidence.