The tongue is an important and a powerful muscle that is involved in various functions like – helping to chew, swallowing, tasting, licking, speaking etc.

Any changes in physical health can express itself through changes in the color of the tongue.

Generally, a healthy tongue is pink in color, either light or dark.  But an underlying disease or infection can cause this pink color to change to black, white, blue, red, yellow.

Source: Cleveland clinic

White tongue

White patches – either thin or thick can be due to varying underlying causes – 

• Improper/incomplete digestion – can be due to viral infections or indigestion 
• Thrust – oral thrush is a fungal infection which can be painful, causing trouble in swallowing.
• Lichen planus – is an autoimmune disease leading to inflammation
• Leukoplakia – growth of precancerous cells.

Purple tongue

Can be due to poor circulation or any underlying heart condition. It can also be due to a rare disease called Kawasaki disease where there is inflammation of the blood vessels.

Yellow tongue

Yellow patch on the tongue can be due to various conditions – 

• Poor oral health leading to bacterial overgrowth.
• Smoking or chewing tobacco
• Psoriasis
• Jaundice

Red tongue

Red tongue could be due to – 

• Deficiency of vitamin B12 or folate
• Scarlet fever – bacterial fever that causes red coloured rash all over the body
• Glossitis –  inflammation of the tongue

Black tongue

Tongue may turn black due to keratin build up. Our nails, skin and hair are made of a protein called keratin. The buildup of keratin may be due to – 

• Poor oral hygiene
• Certain antibiotics
• Chewing tobacco
• Radiation therapy
• Rarely diseases like diabetes or HIV infection

If there is any change in the color of the tongue which remains constant for many days along with other symptoms, it is better to get yourself checked from a qualified health care expert and take the necessary treatment.