Well you have me there….. on the boats this has never come up. In my experience but I can imagine someone popping up and saying… oh, we have green hats on our boat! There is always the exception to the rule of course.
In any given situation what the difference is the colour of your hat going to make? That could be a debate all on it’s own so (to enable this thread to stay on topic) I have started a new thread (Safety hat type and colours?) HERE