Japanese Traffic Lights; Red, Yellow, and ...Blue?

In Japan, people say traffic light colors are red(aka) for stop, yellow(kiro) for caution, and blue(aoi) for go. This was one of the more surprising things when I first came to Japan. The color is the same as in America, so why don't they call it green?

In ancient Japan, they did not distinguish blue and green. And even after the development of the Japanese word for green, midori, in the Heian Period, it was still considered to be "within" blue. Educational materials distinguishing blue and green didn't come into vogue until after WWII during the occupation. Today, most things we think of as "green" are called midori, but still some vegetables and traffic lights are referred to as blue(aoi).

We may think of colors as something absolute; red is red and blue is blue and that's that. But actually, names for colors are completely arbitrary to language and cultural convention. Japan is not unique in this, as there are many Asian and African languages that traditionally do not distinguish green from blue. And on the other hand, colors that in English we call "light blue" and "dark blue" have completely separate names in other languages.

It makes me think of how the Taoist philosophers of ancient China cautioned against words. It's a dilemma; we need words to convey meaning, but words can create reality of their own. Many things we think of at facts, truth, or reality are actually illusions of language. And how we view the world is in part dependent on the language we use. This is apparent in the legal world were words make something real or unreal, fact or false, innocent or guilty. It's well known trivia that the Inuit language of the Eskimos has over 200 words for "snow".  So, it's all good, in America, it's green, in Japan, blue, but we all know when to go.