Short story by Gianni Rodari, I'll try to explain it in english... Forgive me please for the mistakes!!
A traffic ligh in Milan, suddenly became blue. Pedestrians and drivers didn't know what to do. There was chaos reigning. Finally two policemen arrived. One of them started directing the traffic. The other one turned off the traffic light. The blue traffic light had just time to think: "Poor people" I gave them the green light for the sky, if they had understood me, now they would be able to fly. Maybe, they just had fear!"