History

During the pre-internet-dating days, much of the social interaction in the gay community took place in noisy bars. It was simply easier to let others know your desires using color, instead of shouting.

Orange

A bright orange handkerchief worn on the left side means that the wearer is open sexually for "...anything, anytime..." according to Gaycityusa.com. Worn on the right side, the handkerchief means that the person is not looking for anything right now and is only cruising.

Black

Black denotes a man who is into heavy sadistic-masochistic (S&M) intrigues. Worn on the left side, a black handkerchief means he likes to dominate. If the handkerchief is worn on the right side, he's subordinate.

Light Blue

A light blue handkerchief denotes a desire for oral sex, either giving or receiving, depending on which side of the body the handkerchief is located.

Fuschia

A fuchsia handkerchief, in the right breast pocket of the shirt denotes a desire to be spanked. In the left breast pocket, that means the man likes to spank his partner.

Black and White Checkers

A black and white checkered handkerchief represents a person who wants to practice safe sex with a partner. Worn on the right, it means the man wants to be on the bottom. On the left, he likes to be on top.