The concept of color has always intrigued me, and I can pinpoint exactly when the seed of my fascination was planted—even if I didn’t realize it at the time. It happened on a totally ordinary day in a totally ordinary situation in Yokohama, Japan—I was waiting to cross the street. As soon as the light turned green, I overheard a little girl giddily tell her mom, “Ao da! (It’s blue!)”
Wait, what?
Okay, maybe she was just mixing up her color terms, I thought. But then her mom responded, “Ao dane, ikou! (It’s blue, let’s go!)” I double-checked the tiny “go” man on the traffic light—it was definitely green. Eyebrows furrowed in confusion, I started questioning my color vision as I walked. But, in classic Hana fashion (i.e., easily distracted), I forgot about it by the time I reached the other side of the street.
Fast-forward a couple of months, and I was in another totally ordinary situation—at the grocery store—when I noticed the label on a green apple: ao ringo (blue apple). Then, the next morning, I was making my ultra-health drink (which I only make when I’m feeling under the weather because it tastes…healthy), mixing ao jiru (blue drink) powder with amazake, when it hit me: This stuff is definitely green.
I immediately grabbed my phone and started Googling. Either there was something seriously wrong with my eyes, or the entire population of Japan was mixing up their blues and greens!
Turns out, neither was true—but the answer was oh-so captivating.
When blue was green: The evolution of color perception in Japan
So why do Japanese people call green things blue? The answer takes us back about 1,500 years, when Japan began adopting the Chinese writing system.
Back then, colors weren’t divided as precisely as they are today. The Chinese word qing (青)—which is the origin of the Japanese ao—was used to describe a wide range of cool tones, from ocean blues to spring greens. Japan inherited this linguistic trait when it incorporated Chinese characters, making ao the go-to word for many things that we would now call green.
And honestly, this makes a lot of sense. Back then, people were not dealing with LED screens, neon lights, color-coded systems, and endless rows of paint swatches. Their world was shaped by the need to survive in nature, so what really mattered was identifying key differences between broad categories—like light and dark, warm and cool, or natural and man-made. In this context, a single word for a variety of hues was enough.
It wasn’t until Japan’s exposure to Western influences that more specific color distinctions became necessary. The introduction of modern dyes, industrialization, and increasing contact with Western languages led to the emergence of midori (green) as a separate term. However, linguistic habits are hard to break, and ao continued to be used in contexts where English speakers would expect “green.”
This is especially evident in Japan’s traffic lights. When modern traffic signals were introduced, they followed the international standard of using green for “go.” Yet, because of the historical use of ao for green, people continued referring to green traffic lights as ao. To bridge the gap between language and reality, the government even ensured that the green lights used in Japan had a slightly bluish tint—a fascinating example of language influencing perception rather than the other way around.
So, the next time you hear someone call a green light “blue” in Japan, there is no need to question your eyesight—take it from me, it’s just history at play.
