Yeah, back in 2000 they made the courts purple at Indian Wells, Montreal/Toronto, and Cincinnati because they said it was easier for players, fans, and TV viewers to follow the flight of the ball. The move was supposed to be for all outdoor hardcourt Masters Series events, but the surface in Miami remained green. Then, last year, they made a subtle change from purple to blue at those events (the surface always looked more like a really deep blue or indigo rather than a true purple). All events in the U.S. Open Series feature blue courts. Even the U.S. Open went to a blue court. The surface for the Nasdaq, however, has never changed. My guess is that the tournament wanted to keep the courts green to match the green walls and overall surroundings at Crandon Park.