Hi.. Welcome to HEALTHCARE MAGIC.. I have gone through your query and can understand your concern. As per your complain and presentation of symptoms yellowish to orange colour of tongue is commonly not due to any underlying medical condition and is due to improper cleaning leading to deposits of food particles and debris over tongue which leads to bacterial growth and chromogenic bacteria [colour producing] can lead to yellowish to orange colour of tongue.. Nothing to worry, just use a soft toothbrush and very gently clean his tongue. A tongue guard can also be used for the same.. make him gargle with 1:1 solution of hydrogen peroxide and water as it will help in removing debris.. If even then there is no improvement consult a Pedodontist and get evaluated.. Hope this information helps.. Thanks and regards. Dr.Honey Nandwani Arora.