Centre colon on TM1637 4-digit 7-segment LED display?

None of them do. Entirely different protocol and no individual addressing.

Looks nice. :+1:

Were the pin headers fitted to the displays when you received them? The better way to fit them is underneath the board and pointing inward, so the "Dupont" sleeve is neatly hidden and does not poke out from the side.

Did you check that they did not have the wrong capacitors fitted? If they are or 10 nF or more, they need to be removed or you will have erratic operation.