Color of the day (police)
The NYPD Street Crimes Unit started in 1971. During the late 1970s, the 1980s and early 1990s, New York City had a lot more crime than it does today.  Undercover officers were asked to go into the subways in plain-clothes or dressed as a homeless person to hide the fact that they were police. Many of these officers were black and had a fear that as they looked like civilian homeless people that uniformed officers would think that they were criminals if they used their guns. Many of these officers would dress and pretend to be drunk homeless people or as victims in order to catch muggers who were attacking them due to being unable to help themselves. The color of the day system was made to make these officers fear this less and was used by all undercover police officers. At the beginning headbands were given out to each street crime unit member, that were in the color of the day: beginning the use of the color of the day system. Later this included wristbands and today's officers often dress in the color: i.e.: T-shirts, shoes, and hats.