When you approach an intersection and the a traffic light starts flashing green.

It is a sign that the green light is about to change in three seconds.

There is no difference between flickering-green and green light; hence, there is no need to pay special attention to it.

It is a sign that the light turned green a short time ago and you can continue driving.

It is a sign that the traffic light is out of order and you should follow the instructions of the road signs that are placed there.