That, ever since, has created the confusion, the stereotyping and the prejudice. Actually, there are no real secret codes around. What you do is have a certain color handkerchief, partially hanging out of your back pocket, tied around your head or to your jacket. This code is hardly ever used in the heterosexual world. At BDSM parties, codes are sometimes used.
Flat studs indicate submissive.
People who are into erotic power exchange will not only take this very seriously, but many will also consider BDSM a lifestyle and a very important part of themselves and their relationship. Dress codes are frequently used at parties and gatherings. They serve two purposes. One is to keep out everybody who is not supposed to be there. The other is to bring about a more spectacular ambiance.