[1] In 1457, he was created Earl of Argyll by King James II of Scotland, who was grateful for the loyalty of his father during the troubles early in his reign.

[citation needed] The exact date of the marriage is unknown, but in 1460, shortly after the boy-king, James III of Scotland, came to the throne, Campbell was called upon to intervene in a feud in his wife's family.

[13] On 15 January 1472, King James III granted Dunoon Castle to Campbell and his heirs, with the power to appoint constables, porters, jailers, watermen, and other necessary offices.

In the resulting pact, which was to endure until July 1483, a marriage was arranged between Prince James Stewart of Scotland (King James III's son) and Princess Cecily of England (King Edward IV's daughter), a match which did not come to pass due to continued hostilities between the two nations.

[18] Further favors came to the Earl of Argyll in 1480, when the King granted him 160 marklands of the lordship of Knapdale, including the keeping of Castle Sween, for one silver penny in blench farm, i.e., nominal rent.

[20] These lands had previously been held by the King's brother, Prince Alexander Stewart, Duke of Albany, who was in league with the Earl of Angus.

[22] Campbell threw in with the rebels, after Parliament had strengthened King James's hand against the rebellious nobles in October 1487.

[25] Campbell continued in favor with King James IV, and on 21 December 1491, he was one of the conservators of the truce between England and Scotland, which was extended to 1496.

[26][27] One author has claimed that, one reason James III of Scotland has long had a sinister reputation is that "such accounts as we have of him are written by the partisans of his unruly nobles, such as the Earls of Argyll, Lennox, and Angus".

[28] Colin Campbell, 1st Earl of Argyll, died in 1493, and was buried at Kilmun Parish Church on Cowal Peninsula.