wrote in message
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I do find it horrifying that there are people out there driving who
can't tell the difference between a green or red light.

Which is why traffic light heads now have a white rectangle around them so
the *position* of any of the three lights can be inferred in relation to the
rectangle, even if the colour itself is unknown.

Some countries use different shaped lights: eg square for red, diamond for
amber, circular for green in Quebec and Nova Scotia provinces, Canada.