Make some questions and answers as to the traffic light(s) наприклад:-Can

 Can he cross the road when the light is red? -No, he mustnt. He should cross it when the light is green.

Must we cross the street when the light is yellow? No, you mustnt. You should wait till the light is green.

May she cross the street when the light is green?   Yes, she may. She should cross the street when the light is green

Could you cross the road when the light is red? No, you couldnt. You should cross the road when the light is green.