I've seen those three colored lights in action on some school buses. They're confusing as all get out. Good thing that idea died!
Another great invention car companies are beginning to use:
remote keyless entry that instead of flashing the lights, turns on the reverse lights with no brake light. I was driving through a parking lot and saw a large SUV (Yukon Denali) with reverse lights on and no brake lights. Waited... realized the driver was not even in the car. I have seen this on a couple other cars.