and to outdo purple jizz.
It is often used to burn someone really bad, but can also be used as a complement.
If you're trying to pick a chick, it works pretty well, also.
Gina:"how about that guy?"
Kaila:"ewww! Fuck no, i wouldn't fuck that guy if he had rainbow jizz."
Gina:"What about him?"
Kaila:"Oh he's so hot, he's better than rainbow jizz."
As a pick up:
Micheal:"I jizz rainbows."
And the babymaking begins