Thanks for posting query.
Your child probably has a gastrointestinal infection
that leads to fever with greenish stool.
So please follow the advices-Give him plenty of water with ORS, Blunt diet, He may need a course of antibiotics with probiotics and paracetamol
Follow him for development of any warning sign of dehydration
I advise you to get him examined by a Pediatrician
at the earliest, get the investigation done and managed accordingly.
Dr Sourav Ganguly.