When I was so bored playing in a map, I decided to tp to Y coord limit and above, 256 blocks more or less, I pressed F5 being above the limit, then, two things happened: skin was invisible, and the other thing was that sky color changed to blue-green, the second thing I don't know if it's a bug, it happens too without F5; If I'm under the limit I'm not invisible and the sky turns normal.