red hanky
This is typically associated with the gay Hanky Code and if worn on the left, it means that you like to fist guys; if worn on the right, it means that you like to get fisted. UNLESS there is a white stripe and then it just means that you like to shave or get shaved or a black stripe denotes you are or like bears.
I caught Mark at the bar last night with a red hanky on his right arm; I had no idea he was into fisting.