I think if the whole system was redesigned from scratch a lot of things would be different. Why on earth do we use red and green for signalling stop/go when a

I think if the whole system was redesigned from scratch a lot of things would be different. Why on earth do we use red and green for signalling stop/go when a statistically significant number of men (plus a few women) have difficulty seeing those colours? It seems that once you get past a certain level of adoption, it becomes impossible to change even an obviously sub-optimal design.