The 'colors' mentioned in the "Nihon Shoki" are believed to have been blue, red, yellow, white, and black corresponding to the five Confucian virtues (charity, courtesy, sincerity, justice, knowledge), which was based on the Wu Xing (Five Phases).
「当色」は、位階相当の色として、五行思想に基づいた五常の徳目（仁・礼・信・義・智）の青・赤・黄・白・黒が考えられる。