The colors of tongue fur commonly seen are white, yellow and grayish black which may appear singularly or simultaneously. The examination of the colors of tongue fur should be done together with the analysis of the texture, color and shape of the tongue proper.

White tongue fur:
Apart from normal tongue fur, white tongue fur is usually seen in external syndrome and cold syndrome. But white tongue fur is not only confined to external syndrome and cold syndromes.

Thin and white tongue fur is often seen at the primary stage of exogenous disease and diseases due to internal impairment without fever. At the primary stage of exogenous diseases, pathogenic factors attack the superficies but have not invaded the interior, the tongue fur does not have obvious changes. That is why thin and white tongue fur indicates external syndrome. Light-red tongue with thin, white and moist tongue fur indicates wind-cold external syndrome; tongue with reddish margins and tip as well as thin, white and moistless fur indicates wind heat external syndrome. Light-white tongue with thin and white fur is usually seen in internal asthenia-cold syndrome.

Whitish greasy tongue furs are usually due to internal retention of damp turbid substance, phlegm and fluid or due to food retention without transforming into heat. Powder-like thick and white tongue fur that does not feel dry is called powder tongue fur, frequently caused by mixture of exogenous fetid pathogenic factors and heat toxin, usually seen in pestilence and internal abscess.

Yellow tongue fur:
Yellow tongue fur usually indicates internal syndrome and heat syndrome. During the course of a disease, the change of tongue fur from white to yellow suggests that the pathogenic factors have transformed into heat and transmitted to the interior. The yellower the tongue fur, the severer the pathogenic factors. Light-yellow tongue fur indicates mild heat, deep-yellow tongue fur signifies severe heat and sallow tongue fur suggests extreme heat. That is why yellow tongue fur usually appears simultaneously with red and deep-red tongue.

Thin and yellow tongue fur indicates mild pathogenic heat, usually seen in wind-heat external syndrome, or inward invasion of heat transformed from wind-cold, or mild heat progress in internal heat syndrome. Yellow and white tongue fur suggests that the pathogenic factors are transmitted from the exterior to the interior and cold transforms into heat in exogenous disease. Yellow and greasy tongue fur is usually due to accumulation of damp-heat, or due to phlegm and fluid retention transforming into heat, or due to food retention and heat putrefaction. Yellow and rough tongue fur is often caused by pathogenic heat consuming body fluid or by retention of heat in the intestines. But if the tongue fur is yellow, slippery and moist and the tongue is light-white and bulgy, it is due to decline of yangqi and failure of dampness and water to transform.

Grayish black tongue fur:
Grayish black tongue fur suggests severity of internal heat syndrome or internal cold syndrome. The moisture and dryness of the tongue texture are the evidences to differentiate the nature of cold and heat.

Grayish tongue fur is light-black tongue fur. So, grayish tongue fur and blackish tongue fur are the same. The color of the tongue fur corresponds to the degree of the pathological conditions. The deeper the tongue fur color, the severer the pathological conditions. Grayish black tongue fur in cold syndrome usually develops from white tongue fur. For example, grayish black and moist tongue fur with light-white tongue signifies yang asthenia and cold exuberance, or cold dampness and internal retention of phlegm and fluid. Grayish black tongue fur in heat syndrome evolves from sallow tongue fur. For instance, grayish black and dry fur with deep-red tongue or even prickly tongue is due to extreme heat consuming fluid.