In show business, the green room is the space in a theatre or similar venue that functions as a waiting room and lounge for performers before and after a performance, and during the show when they are not engaged on stage.
The origin of the term is often ascribed to such rooms historically being painted green. The modern "green room" is usually not green at all.
The specific origin of the term is lost to history, which has led to many imaginative theories and claims. One story is that London's Blackfriars Theatre (1599) included a room behind the scenes, which happened to be painted green; here the actors waited to go on stage. It was called "the green room". Some English theatres contained several green rooms, each ranked according to the status and the salary of the actor: one could be fined for using a green room above one's station.
Some theories have attempted to identify specific historical origins for the term. For example:
QUINCE: Pat, pat; and here's a marvellous convenient place for our rehearsal. This green plot shall be our stage, this hawthorn-brake our tiring-house; and we will do it in action as we will do it before the duke.
...she took us up into the Tireing-rooms and to the women's Shift, where Nell was dressing herself and...then below into the Scene-room, and...here I read the Qu's (cues) to Knepp while she answered me, through all her part of Flora's Figarys...
In addition to the preceding, there are numerous alternative explanations for the origin of the term green room folk etymologies, including the following: