The color of the day is a signal used by plainclothes officers of some police departments in the United States.
It is used by the New York City Police Department and other law enforcement agencies.
[2][3] A plainclothes police officer will wear a headband, wristband or other piece of clothing in the color of the day,[3] and officers will be told of this color at the police station before they start work.
[6] Undercover officers were asked to go into the New York City Subway and other high-risk areas in plain clothes, or dressed as a homeless person or as a decoy for those victimizing at-risk groups.
Many of these officers feared that uniformed officers would mistake them for criminals in a use of force situation,[7] so the wearing of a headband or wristband colored with the color of the day system was developed to prevent friendly-fire incidents.