My son tj is a nonverbal and autistic. the past few days he has been especially irretable and his bms have been bright green. could this be a virus?

Possibly : It certainly could be a viral infection but given the difficulty with communication he should be evaluated by a medical provider. If he has a high pain tolerance it could be more significant. If it appears to be something other than a viral infection he may need to use antibiotics. I would contact his provider to be seen.

A color change in : An child's otherwise normal stools may mean his intestine is being colonized by new, harmless bacteria. His pediatrician needs to look for physical & neurological changes, x- ray his abdomen (to look for metal objects, batteries, etc.), do an eeg to rule out seizures, do fasting labs (glucose, lipids, cbc, liver & thyroid functions because of his meds) & ask about new stresses at home & school.