Coincidentally, in China's ancient poems, words like "Qingan" and "Qingmo" also appeared. The former, for example, Wu Yun's poem "Wash a face with a girl from Xiao", the third poem "Green temples to reduce worries, red temples to extinguish cries", and Bai Juyi's poem "Daughter" reads "Red gauze slows down green temples". The latter is like Xu Hun's "seeing off guests from the two rivers to the south of the Yangtze River": "I long to leave the sail to meet my old friends, and Qinge is drunk in Hengtang." Green sideburns refer to black sideburns, and green moths refer to women's eyebrows, which are painted in black and slightly green. Dai is a blue-black pigment. Apply to yellow-white skin, slightly dark green.
From blue-black pigment to yellow-white skin, slightly green, I thought of the rules of color matching. In addition to black and white, there are three basic colors: cyan, yellow and magenta. If any two of the three colors are mixed, the other three colors of "seven colors" can be generated: orange, green and purple. The schematic diagram is as follows:
Red → (orange) ← yellow → (green) ← blue → (purple) ← red.
It can be seen that green is composed of cyan and yellow, that is, cyan and yellow. If "green" to the extreme, it is no different from cyan.
But what color is cyan? We all know that "black hair" means "black hair", so "green" means "black" and it is indeed a description of hair (etymology). But "green" doesn't just mean "black", otherwise wouldn't the five colors "green, yellow, red, white and black" appear repeatedly? According to Xunzi's "Blue, Take it from Blue, Blue is Blue", blue refers to a blue thing (meaning the second item of Ci Yuan) and a blue-like and darker color, that is, cyan, one of the five colors (meaning the first item of Ci Yuan). And "green" often refers to "micro-green", such as "green vegetation, meaning newborn, adolescence, youth" (etymological meaning). Therefore, "green" spring must be a kind of "green" spring.
The relationship between green and green can also be found in the meanings of "green silk" and "Ci Yuan". Besides black hair, green silk can also refer to catkins, such as Yu Xin's poem "Peach in the village is pink, willow on the shore is covered with green silk" and Li Bai's poem "Today Bai Liu is lined with green silk". Even "Lv Yun" in Epang Palace clothing not only means that women's hair is dark and thick, but also means "lush foliage". For example, Bai Juyi's poem "Lonely Tung in Yunju Temple" says: "Stand in a blue sky, and Lv Yun in Chiba is inclined." Conversely, "green" also means "green", that is, "black". Such as Li He's poem "Mrs. Gong Bei": "Long eyebrows are green for thousands of years." (Item ② of Ancient Chinese Dictionary)
It can be seen that green and cyan are scientifically related to the traditional culture of China. Therefore, Du Mu compared "black hair", that is, "black hair", to "Lv Yun", which is not imaginary, but a matter of course.