The Green Card is a best practice of Street Soccer USA, used in their National Cup tournaments like the Times Square Cup. The I PLAY FOR league have followed suit and recently introduced it in to their leagues in both San Francisco and New York City.
Typically players would receive red and yellow cards in soccer, due to bad behavior and poor challenges. The Green Card not only rewards good behavior but good sportsmanship too. All green cards given throughout the season will be recorded and the player and team with the most will be rewarded.