Hello, Thanks for your query. This is the yellowish discolouration of all mucus surfaces of the body (including tongue)due to increase of bilirubin in the blood.Jaundice is seen in hepatitis,bile duct obstruction,increased destruction of RBCs and ect. If the tongue or mucous membranes - the membranes containing large numbers of goblet-shaped cells that line the mouth - appear pale this could mean that your blood is lacking in haemoglobin - the iron-containing protein found in red blood cells. This will often result in tiredness and lethargy. Eat a well-balanced diet containing plenty of iron found in lean meat, especially liver. I do hope that you have found something helpful and I will be glad to answer any further query. Take care