A black flag with a horizontal blue stripe represents mourning for law enforcement. It is called the "thin blue line," one of many flags used to communicate different events and circumstances.
Different groups of first responders and military groups have their own flags to represent mourning. Some of these include:
- Thin red line: Firefighters
- Thin orange line: EMS and Search and Rescue
- Thin green line: Park Rangers and Border Patrol Agents
- Thin silver line: Correctional Officers
- Thin yellow line: Security Officers
- Thin white line: EMS
- Thin blue line with a lightning bolt: SWAT
- Thin tiger stripe line: United States Air Force
- Thin blue camouflage line: United States Navy
- Thin green camouflage line: United States Army
Flags of different colors and designs are often used to communicate when out on the open sea. A white flag with a red diamond in the middle signals that the boat or ship is disabled and needs help. A blue flag with a white stripe down the middle signals that the boat is carrying dangerous cargo and is on fire. A boat or ship with a yellow flag that has a blue stripe down the middle is having difficulty steering. A flag made up of a red triangle and a yellow triangle signals that there is a man overboard.