They use yellow flags for penalties, and blue flags to represent a loose ball on the field. Coaches of the teams playing use red flags, which challenge the play that just occurred. Coaches only get two challenges a game (three if they win both the first two challenges), if they are wrong they will lose the challenge and a timeout.
normally it would be black but sometimes depending on the players kit it could be either yellow shirt or green shirt
red or yellow
Black
White
yellow
In the game of soccer, a buzzer flag is a flag attached to a buzzer worn by the assistant referee, which causes a receiver to buzz, warning the referee of the flag's use.
A referee usually controls a football match
Philip Sharp - football referee - was born in 1964.
Jesús Díaz - football referee - was born in 1954.
Football has a referee.
Matthew Breeze -- A-League Football referee in Australia
the rules
Referee's
The referee
In a tournament, there are five referees. There are four flag referees and one main referee. The flag referees raise the flag with the color of the opponent scoring a point. The final decision is made by the main referee.
Flag football or touch football