What color is the official NFL penalty flag?

The official NFL penalty flag is yellow. When an NFL official throws a bright yellow flag onto the field, it signals that a foul may have occurred on the play. The flag is thrown toward the approximate location of the infraction, helping players, coaches, broadcasters, and spectators recognize that officials are investigating a possible penalty.

The color is designed to stand out against the green field and remain visible from a distance. After the play, the referee announces the foul, identifies the team that committed it, and explains the enforcement, such as a loss of five, 10, or 15 yards. A thrown flag does not always guarantee that a penalty will be enforced; officials can pick up the flag if they determine that no foul occurred or if the penalty is declined.

Yellow was not always the NFL standard. League penalty flags were white until 1965, when officials changed to yellow for greater visibility. This can cause confusion with other football codes: Canadian football traditionally uses orange flags, while NFL coaches' challenge flags are red. The yellow object on an NFL field is specifically the officials' penalty marker.