A stoplight is spoken when talking to your wingmen about possible hook-ups for the night.
Green Light- The lady is very attractive, and you should not back down from this possible fling.
Yellow Light- This usually is said when the girl is a toss up. Usually she is turned into a green light after a few drinks. But the next morning you will probably regret it.
Red Light- STAY AWAY FROM THIS GIRL!!! She is ugly, std infested, or might have a boyfriend that is a UFC champion that gets jealous really easily.
Phil: Hey Mike. . what color of the Stoplight is the girl standing over by the bar?
Mike: I would say green light! She looks very sexy, and she has a twin!!