Japanese blue

Alain October 25, 2025 at 6:13 PM · 7 min read

The very first written history of Japan, a mix of fact and mythology, mentions only four colour terms, which mainly stand for the categories of dark, light, bright and vague. Over time these ancient terms evolved into 白 shiro (white), 黒 kuro (black), 赤 aka (red) and 青 ao (blue/green).

This early lack of colour variety, in a people who today pay special attention to the visual side of things, should not surprise us: several studies show that colour is a cultural fact far more than a perceptual one, and that a clear distinction between green and blue appears later in language than the one between white, black and red. So much so that some languages had, and sometimes still have, a single word covering both blue and green.

Even some of the most important classical texts of our civilisation are no exception. Very precise in some descriptions, but not in those about shades of colour. In the Iliad and the Odyssey, for example, Homer uses the word glaukós, which means green, blue and grey, sometimes even yellow or brown. That is why it is used, without distinction, for the colour of water, of eyes, of leaves or of honey.

But let us go back to the distinction between blue and green in Japan.

Towards the end of the first millennium, in the Heian period (794–1185), midori 緑, the Japanese word for green, makes its first shy appearance. But even then it was still considered a nuance of blue! This inevitably created a certain ambiguity. Even today some green things are called with words from the blue family: aoringo 青林檎 (blue apple), which is actually green. Green bamboo is called aodake 青竹 (blue bamboo).

This brings us to the story of the traffic light in Japan, called 青信号 Aoshingoo. The first traffic light was imported from the United States in 1930 and it clearly had a green light. Even so, official documents referred to it with the word ao (blue) rather than midori (green). The linguists’ insistence on the proper term, midori, and the need to follow international conventions on traffic lights produced a compromise. In 1973 the government ordered, by cabinet order, that traffic lights use the bluest possible shade of green: still technically green, but blue enough to keep using the name ao legitimately. While modern Japanese clearly separates blue from green, the idea of a blue that still includes shades of green remains firmly rooted in Japanese culture and language.

Japanese blue

Once again it is a plant that ideally connects us with Japan. Last time it was silphium, an extinct plant whose seed led to today’s shape of the emoji of love. (You will find the incredible story at this link: A heart-shaped emoji❤️ )

This time it is a plant still grown in Japan. We are talking about Persicaria tinctoria, a flowering plant of the Polygonaceae family brought to Japan from southern China: indigo. The blue of the samurai, Japanese blue! 藍 (ai). It is also considered the colour of love, because it sounds like 愛 (ai), love.

Indigo is the oldest plant dye known to humankind, used for thousands of years in places like ancient Egypt, where mummified remains wrapped in indigo-dyed cloth have been found. It reached Japan along the Silk Road around the 8th or 9th century and, like so many other things, soon took on its own unique Japanese touch.

The use of indigo dye in Japan went through three phases: the first, in the Heian period (794–1185), saw it as the colour of the highest-ranking nobility.

The woodblock print Wakamurasaki by the ukiyo-e master Hiroshige shows Prince Genji catching his first glimpse of Lady Murasaki. Court life in the Heian period (794–1185), when the story takes place, was full of dazzling, brightly coloured kimono, but Genji’s in Wakamurasaki stands out because it is a softer dark blue with a white check pattern. It is one of the earliest glimpses of indigo dyeing in Japan.

The second phase came in the 12th century, when samurai wore indigo garments under their armour, because they helped protect the skin from various ailments and kept it cool. Indigo also had antibacterial properties: sword wounds infected by bacteria healed faster.

A less known reason for the samurai’s love of indigo is that its deepest shade is called “kachi” in Japanese. This is also the word for “to win”, which made indigo indispensable for the superstitious Japanese warriors of the time.

The third and last phase came in the Edo period (1600–1868). That is when indigo spread to the masses, so to speak. The Shogun had forbidden ordinary people to wear colours that were too bright, limiting their clothing to muted shades such as blue, brown or grey. Thanks to its beauty and its practical qualities, indigo spread quickly. Cotton and hemp also turned out to be fairly easy to dye with indigo, since only nobles could wear silk at the time.

Soon an indigo craze broke out in Japan, as everyone, from merchants to farmers, who like the samurai found many practical uses in its medicinal (and insect-repelling) properties, began to use indigo almost everywhere in their daily lives. No wonder R. W. Atkinson, a British chemist, saw so many indigo-dyed fabrics, even among ordinary people, when he visited Japan in 1874, that he labelled the colour “Japan Blue”.

Indigo is also fire-resistant and withstands temperatures of up to 815 °C. It proved indispensable for protecting the newborn fire brigades during the terrible fire of 2 March 1657 in the west of Edo (today’s Tokyo)

The Edo period was largely peaceful, and this gradually changed the role of the samurai in society. The Confucian samurai elite was supposed to stay away from “petty commercial concerns”, but a changing economy also meant a changing samurai class. They could no longer ignore their daimyo’s (feudal lords’) interest in trade. Indigo production thus also became a precious export.

Prussian blue

The most famous ukiyo-e print of all, Hokusai’s The Great Wave off Kanagawa (1830–1831), makes very extensive use of blue.

The pigment used is Prussian blue, a synthetic colour imported into Japan from the Netherlands from the 1820s. From then on a real “blue revolution” spread, with woodblock prints entirely in blue called aizuri-e.

The symbolism of blue

Purity

Blue symbolises everything that is pure and clear, like the sky. As in most cultures, purity is a highly valued quality in Japanese culture. Newborn babies are usually wrapped in blue cloth. Blue is also often worn by pregnant women and by women looking for a husband. Blue has a similar meaning in many cultures, probably because of its link with sources of water. It may also be because blue is one of the pigments that can be obtained naturally, especially in Asian countries, from indigo plants. Before the age of synthetic pigments and industrial dyes, indigo was a popular and widely used colouring agent in clothing. For this reason, many auspicious occasions and meetings involved people dressed in blue.

Interestingly, weavers and the people in charge of dyeing fabrics were known to wear white, not blue.

Femininity

Blue is a popular choice for clothing in Japan, and the favourite colour of more than 40% of the population according to a 2019 survey. It is the colour most used in kimono worn by women. Blue is associated with virginity and femininity. This is interesting compared with the Western view, where blue is the colour of men and pink that of women. Western choices for girls and little girls rarely involve blue things. The idea of the ideal woman in ancient times had a lot to do with purity of mind and body. The link between blue and femininity is probably also due to its link with purity and innocence.

In sport

Football

Blue is also the colour of the Japan national football team’s shirt. The players are called Samurai Blue, and it seems the colour was kept because, wearing it, the University of Tokyo team, which represented the country at the Far Eastern Championship Games in 1930, won the first match of the tournament. So over time the blue shirt was kept, in true superstitious Japanese style. Blue is also traditionally considered one of the lucky colours in general.