There are four patterns of tartan authorized by MacCailein Mor, Chief of Clan Campbell and 12th Duke of Argyll.
Campbells of Breadalbane, Cawdor and Loudoun may wear their respective tartans but all Campbells may wear the plain blue, green and black Campbell sett, often in its lighter form sold as "Ancient Campbell" or "Ancient Black Watch".
The sett called "Campbell of Argyll" with a yellow and white stripe is NOT authorized by the Chief.
Clan Campbell of Loudoun Tartan:
St. Francis Xavier University, Antigonish, Nova Scotia
Clan Campbell of Loudon Tartan:
Vrije Universiteit, Amsterdam, The Netherlands