Referees in football, basketball and soccer use a whistle for various signals.
3 referees are in soccer and football
They are technically called assistant referees.
Soccer referees are graded by levels, not by classes. Informally, a referee might be considered "Class A" if they are certified International referees.
If you're talking about soccer referees, I don not believe so.
red or yellow
The answer is obviously. Yes.
The referees are paid handsomely they get 5,000 pounds for the game.