In Japan, what we call the green light is known as “青信号 (blue light).” Yet the actual color is a bluish green, unmistakably closer to green than to blue. If you were to ask, “Is that blue or green?” almost everyone would answer, “It’s green.” And still, everyone calls it blue.
Back in the days of incandescent bulbs, before LEDs took over, the light looked even greener. When I was a child, I couldn’t quite accept that. On my walk home from school, I once pointed at the signal and asked my friend, “Isn’t that green?” She nodded and said, “Yeah, it is.” But still, everyone around us kept calling it “blue.” How curious that was.
The story goes back to 1930, when Japan installed its first mechanical traffic lights at the Hibiya intersection in Tokyo. They were imported from the United States, so naturally, the three colors were red, yellow, and green. In other words, it started out as a green light.
But when newspapers and magazines reported it as blue, yellow, and red, the phrase 青信号 (blue light) caught on among the public.
In older Japanese, the word 青—blue—covered a much wider range than it does today. It included what we now call green. That’s why we still say 青葉 (green leaves), 青菜 (leafy greens), and 青りんご (green apples).
Originally, the legal term for the signal was “green light.” However, by 1947, the word 青信号 had become so common that the law was officially revised to read “blue light.” That wording remains unchanged in the Road Traffic Act to this day.
Then, around the year 2000, Japan began replacing old traffic lights with LEDs. The color shifted slightly toward blue, as if the light itself were moving closer to match its name.
Interestingly, modern American traffic lights are nearly the same bluish-green hue as those in Japan. And yet, Americans have never stopped calling it a green light. The light we see may be identical, but the way we describe it—and thus the way we perceive it—depends on language.
Language doesn’t merely label colors, it defines where we draw the lines between them, and how we feel about what we see.
For the Japanese, 青 (blue) evokes purity, youth, freshness.
For English speakers, green represents nature, safety, calm.
So when that bluish-green signal glows above the street, Japanese hearts see blue, while American eyes see green. The light is the same, but the worlds it belongs to—are ever so slightly different. How fascinating!
