The whole idea of Clan tartans began with Sir Walter Scott and the King of England. The real tradition was wear whatever appealed to a person, what he could afford and the local weavers were making, the more colors the higher the cost. The Black Watch, otherwise known as the Govt Sett, also is a Grant and Campbell tartan as well as being the basis for many others. Frankly, there is no single true tradition on any of it. Personally, I follow the older idea of wearing what I like that I can afford.