<P> A penalty cards are used in many sports as a means of warning, reprimanding or penalising a player, coach or team official . Penalty cards are most commonly used by referees or umpires to indicate that a player has committed an offense . The referee will hold the card above his or her head while looking or pointing towards the player that has committed the offense . The colour and / or shape of the card used by the official indicates the type or seriousness of the offence and the level of punishment that is to be applied . </P> <P> By analogy the term is sometimes used in non-sporting contexts . For example, the UK Radio Authority spoke of issuing a yellow card to those who broke its rules . </P> <P> The idea of using language - neutral coloured cards to communicate a referee's intentions originated in association football, with English referee Ken Aston . Aston had been appointed to the FIFA Referees' Committee and was responsible for all referees at the 1966 FIFA World Cup . In the quarter finals, England met Argentina at Wembley Stadium . After the match, newspaper reports stated that referee Rudolf Kreitlein had cautioned both Bobby and Jack Charlton, as well as sending off Argentinian Antonio Rattin . The referee had not made his decision clear during the game, and England manager Alf Ramsey approached FIFA for post-match clarification . This incident started Aston thinking about ways to make a referee's decisions clearer to both players and spectators . Aston realised that a colour - coding scheme based on the same principle as used on traffic lights (yellow--stop if safe to do so, red--stop) would transcend language barriers and make it clear that a player had been cautioned or expelled . As a result, yellow cards to indicate a caution and red cards to indicate an expulsion were used for the first time in the 1970 FIFA World Cup in Mexico . The use of penalty cards has since been adopted and expanded by several sporting codes, with each sport adapting the idea to its specific set of rules or laws . </P> <P> A yellow card is used in many different sporting codes . Its meaning differs among sports; however, it most commonly indicates a caution given to a player regarding his or her conduct, or indicates a temporary suspension . Examples include: </P>

When was the yellow card introduced in football