A tow truck or towing vehicle must be equipped with flashing or intermittent red and amber lights of a type approved by the commissioner of public safety. The lights must be placed on the dome of the vehicle at the highest practicable point visible from a distance of 500 feet. The flashing red light must be displayed only when the tow truck or towing vehicle is engaged in emergency service on or near the traveled portion of a highway. The flashing amber light may be displayed when the tow truck or towing vehicle is moving a disabled vehicle.