In a lot of old single screen movie theaters, the inside of the projection booth is painted the same way in the same colors. I was told by an old projectionist the reason was the dark green down low would hide the dirt and grime from the projectionist's oily hands and handling the projector carbon rods. The light color green was so the projectionist could see in low light to do his job, but very little light from the projection room would get out into the audience and be an annoyance.