Suggest Treatment For Diarrhea In A Child

Hi, my son is 10 months old and had a vry high temperature dor 3 days (which I put down to teething) now he is off his food and had diarrhea for 4 days which is vry smelly and pale grey in colour. He won t eat any solids but is drinking milk. Please can you advise why it is light grey in colour? Thank you.