The UK cars have this as an indicator as standard and these flash orange by having an orange bulb in clear lamp housing. The twin core wire is simply connected in with the main indicator unit that faces forwards. But to have it lit all the time along with main lights, and have it flash will be hell of a job. You cant buy twin filament 501 type bulbs and even if you did source a bulb you would loose the impact of the flash as the other filament will be continuously lit. Relays at each side could re divert the current as required but would not flash in sequence with main flashers, but wow what a job! If you want them to flash only, just piggyback off the existing wires.