Analysis of information sources in references of the Wikipedia article "Automotive lighting" in English language version.
They are usually operated by pressing a large, red triangle button on your vehicle's dashboard.
To avoid imposing an unreasonable cost to society, NHTSA's lighting regulation continues to allow for the lower cost rear signal (…) Such a configuration can be achieved using just two bulbs and a two color (red and white) lens.
the agency believes improved safety (measured as the reduction in the number of rear-end crashes that resulted in property damage or injury) can be achieved with amber rear turn signal lamps at a cost comparable to red rear turn signal lamp configurations. This is supported by the observation of vehicle manufacturers changing the rear turn signal lamp color for a vehicle model from one year to the next
