i dont have any perks that do that it does it randomly
Then I don't know really.
I went to that place down south-east. Erm... That ex-NCR place with ghouls and radiation.
Anyway, my screen turned green, probably because of the radiation, but when I went back to Novac the screen was still green.
Did you try to restart your game?
That fixed it for me. (With the green tint)