Kanji for Blue

青 (ao / sei) is blue — and famously more than blue, because classical Japanese used ao for the whole cool span from sky to leaf. That is why a green traffic light is 青信号 and fresh greenery is 青々 to this day. 青 also means young and unripe — 青春, “blue spring”, is youth itself; a 青二才 is a greenhorn.

蒼 (sō / aoi) is the darker, wilder blue — the grass radical over a storehouse: vegetation-deep colour. It shades into “pale” for faces (蒼白) and “vast blue” for seas and skies in literary use; 蒼天 is the great blue vault. It is a favourite in modern names (Aoi, Sō) with a cooler, moodier tone than 青.

碧 (heki / midori / ao) is the jewel blue-green — stone radical under king-and-white: 碧眼 is blue-eyed, and the character names the colour of deep lagoons. Rounding out the palette: 藍 (ai), indigo — the dye of workwear and of the proverb “blue comes from indigo yet outblues it”, Japan’s way of saying the student surpasses the master.