blue room

noun2

1. •
   A room with blue (or occasionally green) walls in which effects shots are filmed.
2. •
   (slang) The toilet or washroom on a passenger aircraft.

   • Phyllis Ash was working a flight where the smooth routine was suddenly interrupted by a ten-year-old boy who went to the "blue room" (toilet) and proceeded to get his penis stuck in his zipper. — 1980