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.
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