What is Drink The Rainbow?
1.
A drinking game in which the participants must drink a yellow drink, an orange drink, a red drink, a purple drink, a blue drink and a green drink.
"Hey, do you want to go drink the rainbow?"
"I dunno, last time I did I threw up multi-colours"
See
2.
sit back and toke/ possibly do acid
dude, you are too up tight, sit back and drink the rainbow
