A party where a bunch of girls wearing different colored lipsticks get drunk and kiss a guy's penis until it is a rainbow of colors.
Mike: Man, there were so many girls at the rainbow room last night, it'll take me forever to clean my penis.
Bob: I know, right?
This is much like cherry popcicle
. When a girl who is on her period gives a very willing man head and takes the load in her mouth and holds it there for a while. The man proceeds to eat to eat her out (remember, she is on her period), collecting a delicious load in his mouth. Finally, to top it all off, the two make out and swirl a "rainbow room" around inside their mouths.
"She was really craving a rainbow room, but I refused to put that nasty bloody shit in my mouth."