If a yacht displays their blue or yellow flag from its backstay it has committed an offence and is penalised. This is used where a deliberate or professional foul occurs. This signal isn't used often, usually only in circumstances requiring disciplinary action. Umpires will simply remove the coloured shape displayed for the first penalty. If a yacht has one outstanding penalty, it can be taken at any time during the race after starting and before finishing.
Yachts usually delay until just before finishing unless they get a long way ahead.
If a yacht has two outstanding penalties, the second penalty must be taken as soon as possible. In the unlikely event of a yacht having three outstanding penalties, it receives a black flag and the race is over. The delayed penalty system keeps the racing closer together and makes it more exciting for competitors and spectators.