Most street legal vehicles utilize a combination of three colored lights: white for headlights and reverse lights, red for tail and brake lights, and orange for blinkers....
Mercedes-Benz debuts turquoise exterior lights to indicate the car is self-driving | A visual indicator for other drivers::undefined
because the're mostly tested under extremely safe conditions, and current self driving regularly asks you to take back over (you also have to still pay attention and have your hands on the wheel) which makes it level 2. by definition, the human is driving.