A code used by the homosexual community to let others know what they're "into". i.e. if a boy wears a light blue hanky in his back pocket, that means he's into oral sex.
Hey, the hanky code says that guy would be into you!
Wearing a colored hanky to identify sexual preferences within leather, or BDSM community. The color dictates your interest(s).
Black: Paingames, Whipping
Dark Blue: Fucking
Which pocket is also important: left = top, right = bottom
Mike: Hey Jimmy, why does Paulie have a red hanky in his right pocket?
Jimmy: Oh that? He just wants some guy to stick his fist in his ass. That's his hanky code.
Mike: Well why do you have a brown one in your left pocket?
Jimmy: Go away.