Why are traffic lights green for go and red for stop?

Question

What is the origin of those colours?

Answer 1

It dates back to the days when travelling by boat was one of the main forms of transport. Ships always have a green light on the starboard side and red on the port side - mostly because they were the only colours of glass you could get in those days. All ships pass starboard to starboard, therefore it came to be known that green means go. The system was used for railway lights before traffic lights became commonplace.

Answer 2

Red is a sign for danger and warning for traffic and green is to do with hope significnace of safety.