OK, how about the green arrow in the instrument and the red hazard light?
Recap is:
1) The green instrument arrow light blinks in synchrony with the external markers when everything is OK. The frequency may be affected by the load.
2) If the load is not sufficient (open circuit, bad contact, burned bulb) then the other external marker will work but the green indicator will not. The bulb is in series with the coil of the relay that drives the indicator.
3) The emergency flasher internal red light flashes as the opposite of the external lights because it is connected between 12V and the bulb. When the external bulb is ON there is 12V on both sides of the red light and no light. If there is no load at all (open circuit) the red light will not illuminate.