Perhaps you are thinking of the streets or properties in the game? Monopoly features 22 properties divided into eight color-coded groups:
* Brown: Mediterranean Avenue, Baltic Avenue
* Light Blue: Oriental Avenue, Vermont Avenue, Connecticut Avenue
* Pink: St. Charles Place, States Avenue, Virginia Avenue
* Orange: New York Avenue, Tennessee Avenue, St. James Place
* Red: Kentucky Avenue, Indiana Avenue, Illinois Avenue
* Yellow: Atlantic Avenue, Ventnor Avenue, Marvin Gardens
* Green: Pacific Avenue, North Carolina Avenue, Pennsylvania Avenue
* Blue: Park Place, Boardwalk
Each group of properties has its own set of rent costs and house/hotel prices.