Green room

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, during, and after a performance or show when they are not engaged on stage. Green rooms typically have seating for the performers, such as upholstered chairs and sofas.
The origin of the term is often ascribed to such rooms historically being painted green. Modern green rooms need not necessarily adhere to a specifically green color scheme, though the theatrical tradition of the name remains.
Some English theatres contained several green rooms, each ranked according to the status, fame, and salary of the actor: one could be fined for using a green room above one's station.
Possible sources of the term.
The definitive origin of the term is lost to history, which has led to many theories and claims, including:
"Tiring houses".
In Shakespeare's day, the actors waited in a "tiring house" probably because actors were attired (put on or changed costumes) in this space. Here it is mentioned by Peter Quince as he plans for his acting troupe to rehearse in the woods:
Samuel Pepys mentions these locations at the Drury Lane Theatre Royal in 1667: