This article says that Colman was born at Argyll in about 516 and died about 610.

First bishop and patron saint of Dromore. Born in Dalaradia c. 450, date of death uncertain, feast day 7 June.

Article suggests that Colman founded a monastery in Dromore in about 514, and died mid-sixth century.

From Alban Butler's Lives of the Saints. This article weighs in with the opinion that the saint was born in about 516 and died around 610.