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A friend of mine who is (completely) red/green color blind once told me that he can distinguish the green traffic light from the yellow and red one despite his color blindness and that he thinks to be able to remember having heard that this is not an accident. Is there some law or guideline for it or is it just niceness on the traffic light manufacturer's part and what exact green is it?

In case it matters, I'm living in Germany.

(Sorry, if this is the wrong SE; it seemed like the most appropriate one.)

zvavybir
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I am red-green color blind. I researched and blogged about this years ago. Since then, the primary sources have disappeared off the internet, except for the official CIE standard, which is expensive. So unfortunately you may have to take my word for it.

Green traffic lights are are slightly toward the blue end of the spectrum, which lets people like me differentiate them from red lights. There is some variation in the allowed color range, but they are all distinct from the pure green that's hardest to tell from pure red.

David Leppik
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Red-green color blindness is a reduced ability to see color. It's not total. Traffic lights are not all the same color. LED and incandescent traffic lights look slightly different.

stretch
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I am red green colorblind too, and 72 yrs old. I first realized I had this issue when I was about 10 yrs old, and it motivated me to do a school report on the subject. What I found back then was that the green lights were designed with a frequency shift to make them easier to see for colorblind people. They still look a color of green to most people, but to me they look almost white, so they are easy to tell from the red lights.

Rich Bates
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