You can accomplish it quite easily with variables, the bullet object and animation.
Create a traffic light sprite, three frames for each light.
Create your pedestrian sprites, add the bullet behaviour, initial speed set to 0.
Simple bool variable, when the traffic light sprite is green, the bool becomes true. Separate event, conditional of bool being true: Results in pedestrians having set speed to 30, 300 etc. whatever feels good.
You could make it more complicated by having a numeric variable, each light represented by a number, and have a few pedestrians cross on amber.
The real confusion is why there's a zebra crossing and traffic lights!
Hope that helps, traffic lights can actually get very complicated from a programming perspective if you want to do them properly (With a real logic system controlling a city for example.
Just thinking about it brings back memories of Flowol... Ow.