Dan (丹 cinnabar) and qing (青 cyan) were two colors frequently applied in traditional Chinese painting. Cinnabar is red and cyan is bluish green. In early times, Chinese paintings often used minerals such as cinnabar and cyan to draw lines or fill in colors. Hence the term danqing (丹青) made from the combination of dan and qing could stand for painting in general. Representative works of this kind included silk paintings unearthed at Tomb No.1 of Mawangdui of the Han Dynasty as well as the Dunhuang frescoes of the Northern Wei period and the Sui and Tang dynasties. Later, colors made from cinnabar and cyan were gradually replaced by ink and wash. Partly because of their bright, contrastive colors, and partly because mineral colors do not deteriorate appreciably over time, people used red-character books to record merits and bluish-green-character books to record historical events. Historians often use danqing to refer to a man’s outstanding, indelible work that deserves to be put down in history.

Gu Kaizhi was particularly skillful in painting. The figures he portrayed are amazingly vivid and lovely. Xie An held him in high esteem, and regarded him as superior to all other artists, past and present. (The History of the Jin Dynasty)

Thus a painter portrays a person’s physical features, just as a historian records his accomplishments. (Cao Pi: A Letter to Meng Da)