Nothing to do with emigration to the USA http://www.bbc.com/sport/0/football/34162999 Green cards: Italy's Serie B to reward positive player behaviour Green cards will be used by referees in Italy's Serie B this season to reward instances of fair play during a match. The cards will not be handed out during matches but will be a "virtual" card given to players for positive behaviour.
That's a great idea, collect a few greens and then when an opponent really pisses you off you can twat him one good and hard, then use your greens to offset the red. Or have I miss understood.