A man was stabbed on a southbound E train Friday by a woman with blue hair, police said.

The pair were on the train around 5 p.m. near West 42nd Street and Eighth Avenue when the woman stabbed him, cops said.

She remained on the train while the victim got off to get help from police.

Authorities said the relationship between the victim and the suspect, and what led to the altercation, is unknown.