Actually the thing I hate the most is going to a public toilet, or the toilet at work, just any toilet which has this little nice helper just below the handle: green means available and red is shown if it is occupied.
Now think of this situation: You really have to go to the toilet. Finally you can find the public toilet which has 100 toiletboxes. All doors are closed. You pass by to search the one and only which is available. Ok. With a normal color vision, you just rush along the boxes and turn the last green to red. And me? I walk along and recognize, that I can’t see the difference between available and occupied. I look closer, but no way to see any difference. I start listening, maybe I can find the one. Finally I start pushing every, really every handle down to find my way through to the green-one with people yelling at me: “Hey man, cant you see, it is occupied.” Just to finally find out after a long walk that none of them is available.
Yes I know. It’s not like that. But almost. Really. I walk pass the doors and try to find out which ones are occupied and try to find the available ones. I’m always relieved if doors cant be closed if they are not locked or if it is written down in small letters: occupied – available.