Colman became the third abbot-bishop of Lindisfarne in 661, succeeding Saints Aidan and Finan. Like them, he had come from Ireland to become a monk at lona, and he wholly favoured Celtic custom in such matters as the dating of Easter and the tonsure of monks. He had the support of Oswy, king of Northumbria, but Oswy 's queen, Enfleda, came from Essex and favoured the Roman Church's practices. In 664 Oswy summoned the Synod of Whitby to decide the issues. Colman was defeated in debate by Saint Wilfrid of Ripon and resigned.

He returned to lona, accompanied by his Irish monks and by thirty English monks, but then decided to settle in Ireland. Divisions soon appeared at the new monastery on Inishbofin, an island off the coast of Co. Galway. The English monks complained that the Irish visited the mainland in summer, leaving them to bring in the harvest alone. Colman solved the problem by establishing a new foundation for the English monks on the mainland. He died on Inishbofin in 676. Roman practices had already gained sway in southern England, and Colman's defeat at Whitby presaged the gradual decline of the Celtic Church, though in Ireland Roman authority was not fully established until the twelfth century.

From the Appletree Press title: A Little Book of Celtic Saints.