why would your tongue be yellow
Yellow tongue usually occurs as a result of a harmless buildup of dead skin cells on the tiny projections (papillae) on the surface of your tongue. Most commonly this occurs when your papillae become enlarged and bacteria in your mouth produce colored pigments.
Rarely, yellow tongue may be a sign of jaundice, a yellowing of the eyes and skin, which sometimes indicates liver or gallbladder problems. Self-care is usually all that's needed to treat yellow tongue, unless it's related to another medical condition.