An early origin tale known as Conall Corc and the Corco Loígde, which survives only as part of the Irish genealogical tract in MS Laud 610, includes a few brief notes on the saint.

This text was probably written at Colmán's foundation of Cloyne and though it cannot be precisely dated, a rough approximate of c. 700 or earlier has been suggested.

[3] This prominence accorded to the Éoganachta in the genealogies is to be seen in the light of Colmán's monastic career and the position of Cloyne after his death (see below).

The text Conall Corc and the Corco Loígde includes a brief triad in which Colmán is named as one of the three "ex-laymen" (athláich) of Ireland, along with Énna of Aran and Móchammac of Inis Celtra (though it also adds a fourth, Bishop Erc in Sláne of Mag Breg).

[7] The origin legend Conall Corc and the Corco Loígde claims that the land for the foundation was not given by the local king, but by Coirpre (Crom) mac Crimthainn (d. c. 580), who was king of Munster from the Eóganacht Glendamnach:[8] Aired Cechtraige has been identified as the later parish of Erry in the barony of Middlethird, and Cell Náile as that of Killenaule, in the barony of Ardagh, both in the diocese of Cashel.

[3][9] Earlier in the text, Colmán is also said to have uttered a curse (maledictio) which brought down the walls of the city of Ress or Ressad.

The cathedral and round tower are situated on a limestone eminence in the midst of the valley, surrounded by rich meadows.

[11] Further details of his life are not documented in writing but the connection of many places in counties Cork and Limerick with his name to this day proves the reality of his labours.

Colman then went to the school of Saint Iarlaithe of Tuam and after his studies, he is next mentioned as preaching to the heathen population in the east of County Cork.

After the king's death (c. 580) Colman somehow became involved in factional strife between Coirpre's descendants in which some of them persecuted him while others, the ancestors of the later dominant line, protected him.

[1] He died on 24 November (his subsequent feast day), circa 600, and his probable place of burial is Cloyne, where he may have left a school of poetry in existence.