A native of Monalena, Co Limerick, prior to the Easter Rising Colbert had been an active member of the republican movement, joining both Fianna Éireann.
As an active member, he is said to have worked with incredible energy in educating the boys, each night holding classes in signalling, scouting, and map reading. Colbert was known not to drink or smoke.
Later he became a captain in the Volunteers and Pearse spoke of him as “Gallant Captain Colbert”. Colbert was in command at the Marrowbone Lane distillery when it surrendered on Sunday, April 30, 1916. His execution took place on May 8, 1916, age 23.