I worked with a low voltage electrician who turned out to be colour blind. A termination was bad and I found a category cable had an orange and a brown wire swapped. I showed him the termination so that he could see I found the problem but he didn't see what was wrong with it. I jokingly asked if he was colour blind and he responded "Yes and if you tell anyone, I will kill you" only half jokingly. Turns out, he was incredibly self conscious and defensive about his colour blindness and he tended to swap the orange and browns around once out of a couple hundred terminations so I'd always go in behind him and double check his cabling and fix it for him if one was bad. Other than that, he was a brilliant electrician and had been doing it for several decades, so he got on just fine.