A normal, healthy tongue is pink, moist and dotted with taste buds. Healthy tongues also have a light coating. Any deterrence from these normal symptoms may indicate that something is medically wrong.
Tongues can take on a variety of shades, textures and moisture levels depending on their health condition. Since tongues are living tissues, they can contract bacterial, fungal or viral infections. These infections can cause the tongue to turn a dark color, have a white coating or be very painful. Other conditions that can affect the appearance of a person's tongue include thyroid disease, oral cancer or nutritional deficiencies.