When a girl is on her period and a guy licks her out.
Can also be when a guy licks out a girl when on her period and he kisses her after licking the pussy and transfers the period blood back into her mouth.
Only a real whore would attempt this.
1. I just gave this girl a rainbow kiss
2. You are fucking disgusting!
1. Never try a rainbow kiss, you will throw up
2. I know, me and this whore did it last night and we threw up in eachothers mouth !