Born in the townland of Moanleana, Castlemahon, County Limerick, he was the fourth youngest of thirteen children[4] of Michael Colbert, a farmer, and Honora McDermott.

Colbert continued his education at a Christian Brothers school in North Richmond street.

[9] In 1912 he became head of an Irish Republican Brotherhood (IRB) circle within the Fianna started by Bulmer Hobson.

[12] It has been claimed that when the order to surrender was issued, he assumed the command of his unit to save the life of his superior officer, who was a married man.

[3] However, this seems to have been a matter of luck - the well known Colbert was picked out immediately by Dublin detectives who had often seen him drilling Fianna Éireann and speaking at anti-recruiting meetings.

He handed her three buttons from his volunteer uniform, telling her "They left me nothing else," before asking her when she heard the volleys of shots in the morning for Éamonn Ceannt, Michael Mallin and himself would she say a Hail Mary for the souls of the departed.

The soldier who was guarding the prisoner began crying according to Mrs. Ó Murchadha, and recorded him saying "If only we could die such deaths.

[16] In May, one hundred years after his execution a full-scale limestone sculpture of him was unveiled at the gable of his one-time house in Moanlena, County Limerick.