We are going to (eventually) colour code our Allen keys with shrink wrap so you can tell the small ones apart from the big ones, as well as so they don’t get mixed up at competitions.
I am wondering what colours other teams use that do this as well? It might be interesting if there are some combinations that seem more popular.
To add to what has been said here, I have found spray painting the wrenches (masking the ends) has worked well.
You can also buy after market wrenches in say gold or chrome to help them stand out.
Something related that I have done is used after market screws with socket-cup heads for in-between sizes like 3/8th inch long screws to help tell them apart. (yes this is legal)
We use red tape for large and white tape for small, but they don’t stay on very long we are both too busy and lazy to re-colorize them again… the shrink wrap idea is really good though
We have put yellow electrical tape on the small allen wrenches. Since the tape comes off easily, I normally look for residue or lack thereof.
Basically, I do not suggest tape, but I am not sure what else works.