Red or green?

The most common form of color blindness is red-green blindness

A friend of mine here in Gothenburg is color blind and can’t see the difference between red and green. I thought this would be a big problem when you’re driving a car for example, but he says that it’s definitely going to a public toilet that is most stressful for him. He explained that he can never tell if it’s occupied or not. At first he pulled on the door and found out that way whether someone was already in there or not. But whenever somebody was already occupying a stall, they got so irritated by him that he has now switched strategy. Now he always knocks to see if it’s free or not.