Why do they call the green room green, when its not green?

So my mom is in florida and she is a helper for her friend thats works to sell these cookies. So I called her and she was in the green room and I asked "what's a green room" then she gave me an assignment. First let me explain what a green room means. A green room is a room where actors or actresses stay when they are waiting to get on stage. In whatever time period the term was made it was erased but now we have tons of theories about it. And this is one of the theories. Many actors are scared before the go on stage, a person with nausea is often said to look green, so the green room is where the actors wait before they go on stage. Thats one of the many theories. If you want to read  more of them, just click here https://en.wikipedia.org/wiki/Green_room