HANKY CODE - White: Masturbation
HANKY CODE - Blue: Anal sex
HANKY CODE - Red: Fist
HANKY CODE - Black: BDSM
(also known as handkerchief code or bandana code) is a color-coded system employed in the gay leather and fetish community to indicate preferred sexual fetishes and roles.
It is thought that the modern hanky code started in New York City in late 1970 or early 1971 when a journalist for the Village Voice joked that instead of simply wearing keys to indicate whether someone was a “top” or a “bottom”, it would be more efficient to subtly announce their particular sexual focus by wearing different colored hankies.
Check Wikipedia for more information: https://en.wikipedia.org/wiki/Handkerchief_code