Long before we can see above the car’s dashboard, we are taught that green signifies going and red indicates stopping. This is an internationally understood concept. traffic light The color scheme is standardized across much of the globe. However, if you've visited Japan (as I have), you may have observed that some traffic signals appear slightly bluer than green—plus, even the clearly green ones are often referred to as... as ao (blue) rather than midori (green) in Japanese.
So why Are traffic signals seen as blue in Japan? In front of us, Makiko Yamagata, a native Japanese speaker residing in Nagoya, Japan, and Katsuhiro Ito, another native Japanese speaker and an authority on language and culture, discuss the background and subtleties related to Japan's "blue" traffic lights.
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Why do traffic signals appear "blue" in Japan?
Understanding the Japanese language and history can shed light on why green traffic signals in Japan are referred to as blue. "In old Japanese, there were only four color terms: red, black, white, and blue," explains Ito, a Japanese language instructor with over two decades of experience. "The word" ao was employed to describe a variety of hues, encompassing what is currently recognized as green." In earlier times, if someone wished to characterize something as green, they would employ the term used for "blue." This method remained in place until the Heian Period (794-1185), when the word... midori (associated with the colors of nature and lush vegetation along with energy) began being used to define what we currently recognize as green.
Ito notes that a restricted set of color words was not exclusive to the ancient Japanese language—it was common in numerous languages historically. Even though languages later developed additional ways to describe colors, traces of this early system remain visible in contemporary speech. "As a leftover from that time," Ito explains, "things that are green are occasionally still called 'ao.'" (Find more details below.)
Although this frequently confuses outsiders and those learning the language, it is completely typical for native speakers of Japanese. "For us, it's very natural to refer to specific green objects as blue," explains Yamagata. Indeed, it's deeply rooted, and she mentions that she only became aware of the confusion regarding the color of traffic lights. after Her international friends inquired about it.
Although "go" traffic signs in Japan typically use green or a bluish-green color, and the old era of categorizing colors with only four labels has long passed, Yamagata states that there isn’t stop sign visible when it comes to utilizing apparent when it involves employing evident when referring to implementation noticeable when discussing usage clear when talking about applying obvious when considering utilization present when dealing with application discernible when addressing use observable when concerning deployment explicit when regarding operation ao To describe green traffic signals. "I still refer to them as blue, and I tell my children they're blue. So they'll likely continue moving forward as blue!"
Where did Japan's blue traffic signals originate from?
Japan's traffic signal colors have historically mirrored those used globally — red indicating stop, yellow signaling caution, and green meaning go. However, linguistically, the green light in Japan has traditionally been referred to as ao shingou (the blue signal), and in certain areas, it indeed looks more blue than green.
The glo The established standard for a green light signaling "go" was determined by the Convention on Road Traffic Sign and Signal Agreement International Treaty for Road Signs and Signals Global Accord on Road Markings and Signals United Nations Road Safety Regulations Treaty Worldwide Framework for Traffic Control Devices Transnational Standards for Road Guidance Systems International Code of Practice for Road Signage Agreement on Uniformity of Road Warning Symbols Treaty Governing International Road Communication Marks Concordat on Standardized Road Indication Methods In 1968, certain nations, including the U.S. and Japan, did not sign the treaty, which means there may be different versions of the typical red, yellow, and green traffic signals.
When traffic lights were initially implemented in Japan during the 1930s," Ito explains, "the green signal was occasionally referred to as 'green,' similar to how it is known in other nations." However, following World War II, the Road Traffic Act of 1960 defined the traffic light as 'ao,' and this term has been used consistently thereafter.
However, the change sparked some debate. Certain linguists objected to still labeling green lights as blue, while international traffic guidelines set the standard that the signals should truly be called green. At the same time, Japanese people had grown used to calling them blue. This led to a conflict. Japanese linguistic tradition and routine aligned with global benchmarks and contemporary terminology. In 1973, the Japanese government sought to resolve the matter once and for all. A ministerial decree mandated that traffic signals use a specific hue of blue-green— Just green enough to satisfy worries regarding international airport customs, but blue enough to still be referred to as "ao." The regulation appeared to address the problem on paper, but it keeps confusing visitors and those not familiar with the Japanese language.
What other things could be referred to as blue but are actually green?
Traffic lights aren't the only visual green element called "blue" in Japanese. Several other terms and expressions also contain this reference. ao , such as aona (green leafy vegetables). Here are additional examples that Ito and Yamagata provided regarding items that appear green visually but have blue explanations in Japanese:
- aoringo : green apple
- aotake : young bamboo
- aota : a paddy field with unripe green rice crops
- aonori : A green variety of seaweed that looks vibrant, often used as a topping for various hot Japanese dishes, like okonomoyaki (a savory pancake)
Ao may also indicate that something is youthful or recent, Yamagata explains, "so items referred to as 'ao' are not always literally blue." Aoba For instance, it literally means "blue leaves," but the term refers to young green leaves, according to Ito. "Fresh looks are also described as 'aoi' or 'aoaoshii' (fresh or greenish)."
Ito states that these examples illustrate how the term has evolved into various semantic areas. "For example, since" ao refers to the color of young leaves, it is also metaphorically used to mean immature or inexperienced.” In Japanese, you can say “kare wa mada aoi” to mean “he is still inexperienced.” Notice that the “ao” at the end of the sentence technically means blue, yet it is understood in the same way we say someone is “green” in English to express that they’re young or inexperienced!
Ito mentions that similar phrases can be found in Japanese, like "tonari no shiba wa aoi" (meaning "the grass is always greener on the other side"), where "green" is implied even though the word for "blue" is technically used.
So, are the traffic signals in Japan? actually blue?
Traffic signals are labeled "ao" (blue) linguistically In Japanese, but not necessarily visually. Even though you may notice traffic lights in Japan have a bluish tint instead of the usual green seen in many other countries, they are typically considered visually green but called "blue" in the Japanese language. If Japan is on your... travel list and when you're in a vehicle with people who speak Japanese natively, keep this in mind: Ao —not green—means go!
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Sources:
- Makiko Yamagata, a native Japanese speaker; email interview conducted in May 2025
- Katsuhiro Ito, a native Japanese speaker and instructor of the language; email interview conducted in May 2025
- Tenyomi : “Green”
- United Nations Treaty Collection International Agreement on Traffic Signs and Signals
- Japanese Law Translation : “Road Traffic Act”
- JapanUp! Why do traffic signals appear blue in Japan?
