It all started back in the early 70's with an article in the Village Voice.
The Village Voice is an alternative paper that has been published in New York's Greenwich Village since 1955.
They published a story saying that gays in the bars in the village would have an easier time picking each
other up if there were a better system than keys left and right. They suggested going to the surplus store at Christopher and Washington
and buying the Levi bandanas. There were only a few colors suggested: red, navy, light blue, green, black; because that was all
there was for sale in that store at the time. The article was meant as a joke, but the community took it to heart.
Shortly after that bandanas started to appear in back pockets all over the Village. Over time, more colors were added
and use of the "hanky code" spread beyond New York.