Treatise on the Channels and Collaterals

The Yellow Emperor asked: When the collateral vessels become visible, their five colors differ—there are variations of green, yellow, red, white, and black. What is the reason for this? Qi Bo replied: The main channels have fixed colors, but the collateral vessels have no fixed changes. The Yellow Emperor said: What are the fixed colors of the main channels? Qi Bo said: The heart is red, the lung is white, the liver is green, the spleen is yellow, and the kidney is black. These all correspond to the colors of their respective channels.

The Yellow Emperor said: Do the yin collaterals and yang collaterals also correspond to their channels? Qi Bo said: The colors of the yin collaterals correspond to their channels, but the color changes of the yang collaterals have no fixed pattern; they vary with the succession of the four seasons. When cold qi predominates, qi and blood become congealed and rough; congealed and rough, they appear green-black. When hot qi predominates, qi and blood become slippery and moist; slippery and moist, they appear yellow-red. These are all normal colors and are called absence of disease. If all five colors appear together, it is called cold-heat disease. The Yellow Emperor said: Well spoken.