A red card, or ejection
A warning, indicated by a verbal admonishment, or a caution, signalled by showing a player or substitute a yellow card.
3 referees are in soccer and football
Green card in soccer means that when a player respects the referees' decision and be a sportsmanship person
When a football player gets a red card or yellow or out of bounds.
They are technically called assistant referees.
The referee can warn a player in two ways: a verbal warning, or a yellow card.
The Official, besides being able to Caution a player with a Yellow Card or Expel a player from the field (Red Card), may also choose to warn the player of what he feels is not reckless or dangerous enough to warrant either a yellow or red card. Usually this means listening to the Referees reasoning of why he/she is warning you.
Soccer referees are graded by levels, not by classes. Informally, a referee might be considered "Class A" if they are certified International referees.