Something else about color

Something else:

I was walking that day and I reached a cross of the streets. Cars were rushing in one unstoppable flow. It was very dangerous even to think to cross the street on red colour of traffic light. The very second I noticed red my body intuitively stoped.  I was thinking about colours. Suddenly thought came to my head: “What if someone from middle ages appeared here in our century and that someone faced this overcrowded with traffic street. I think the speed of big moving objects would give a sense of fear and will prevent that person to cross the street. However would that human being react accordingly when the red light will change to green? Will the color make its job or it gained too much meaning in our century? Is it so instinctive that red is danger, as it related to blod probably.  Then green what? Fresh? Nature? Why go?