Parties where you're only allowed to wear either red, yellow (amber) or green depending on how willing you are to make out with someone.

Of course, there's more fame (for the boys) related to wearing green and pulling a red girl than the opposite. Sadly, I haven't ever been to one myself - but I'd like to come - probably wearing a green hat, yellow shirt and red pants (you can kiss with me - maybe I'll allow you to put your hands on my naked skin, but there's no way I'll have sex with you (of course, there's nothing I'd like more - but it's all about the signals, right?)).