The oldest surviving written records in the Japanese language of ordinary people are the Manyō-Shū poems, which date from approximately 750 (original text: Frellesvig, Wright, Russell, & Sells, 2016 ; available in translation: McCauley, 2001a ; reviewed in English: Stanlaw, 2007 2010 ; Conlan, 2005 ). The color terms ao (blue) and midori (green) existed side by side in this early period, and their uses were not well distinguished. For example, in the Manyō-Shū poems, the color term awo (precursor to the modern ao) was sometimes used to name the colors of things that were clearly gray (a dappled gray horse [poem 136]), things that could be either green or blue (seaweed [poem 131]; mountains seen in the distance [poems 688, 923, 2707]), or things that were clearly green (leaves [poems 16, 2177]; grass [poem 2540]). Awo was also used frequently in the phrase “()” (“auspicious blue, vermilion [red] clay”) as a metaphorical, honorific reference to the capital city Nara (over a dozen poems, including poems 29, 128, 1046, which are available in translation [McCauley, 2001a ], and poem 328, which is most famous [Haitani, 2007 ]). Awo was also used for clouds (e.g., poem 3329; Nippon Gakujutsu Shinkokai, 1965 , pg. 311) which were probably intended to be blue rather than green. Midori was used less frequently in Old Japanese, but it too sometimes meant blue, sometimes green. In a poem dating from 1192, midori named the sky (midori-no-sora), which was clearly blue (McCauley, 2001b ), but in Manyō-Shū poems 2177 and 2540, midori named the color of summer leaves and grass, respectively, which were clearly green. Whereas ao continued to be used to name some green things as well as blue things, and sometimes black and gray things as well, over the next centuries midori became restricted to green. During the Meiji era (1868–1912), ao generally came to mean blue rather than green (e.g., a poem by Wakayama Bokusui, translated by Rimer & Gessel, 2005 , pg. 311), but in a holdover from its previous meanings, ao is still used today as the color of fresh green shoots and the green traffic light. Contrary to these specific instances where ao denotes certain green things, the present results and the results of other studies indicate that modern Japanese is not a grue language: Like modern English, the usual word for blue (ao) covers only blue samples ( Figures 5 and 6 , and the green histogram in Figure 8 ), and phrases like midori-no-sora sound strange to the modern ear. The modern Japanese use of ao to name certain specific green things is best attributed to custom and cultural connotation, perhaps analogous to the English use of blue to name the color of the blood of an aristocrat.