(Suggestion for upcoming V9 event system)
Simple really, you hit an event and it tints your screen what color you select it to. Black is for night, green is for radioactive, exc. Handy as we would not need to worry about using laggy dark lights to fill up a cave, just put a screen tint at the beginning and the cave it dark! I'm guessing it would have to be directional (north-black, south-clear) to stop glitches.