Flagging

The Handkerchief Code was a form of flagging which evolved in the early 1970s, but wasn't formally codified until its inclusion in the 1983 edition of The Leatherman's Handbook. It has since expanded to include many different colours, patterns, and Kinks. 

The positioning of the handkerchief meant as much as the colour. Those worn on the left indicated an active or dominant participant. Those worn on the right indicated a passive or submissive participant. Despite its visual language, flagging still required some discussion between partners before play. 

Flagging was far more popular before the advent of hookup apps, and was an easy way to communicate what you're looking for while cruising. Each colour bandana indicated a different kink. 
Black: S&M, Dark Blue: Anal, Light Blue: Oral, Orange: No Limits, Green: Sex Work, Yellow: Watersports, Brown: Scat, Purple: Piercing, Red: Fisting, Grey: Bondage. 

This small learning project was made using an Awesome Tuts tutorial and a lot of spaghetti code.