Hello, I can understand your concern. You are right in your assumption that the green color of tongue might be due to fungal infection or thrush. As your son has been on antibiotics for the throat infection, the antibiotics might have changed the normal flora of the oral cavity infecting the tongue with fungal growth. The infection might resolve on its own as the throat infection will resolve and the antibiotics course will complete. Thus, he may not need any treatment. If it does not resolve after completing antibiotics course, your son can be prescribed antifungal medicines based on his age and weight. I would also recommend to maintain adequate oral hygiene. I hope this information helps you. Thank you for choosing HCM. Let me know if you have follow up questions. Best, Dr. Viraj Shah