green room 
noun
A room in a theatre or studio in which performers can relax when they are not performing.In fact, he rarely gets a speaking role so spends most of his days stuck in a green room with other extras, envying the A-list stars....
- When I got backstage for the interval the green room was still fairly quiet.
- The more sanguine can be found in the green room, drinking cups of tea, gossiping and smoking with other equally sanguine cast members and eternally bored understudies.