I read the Black Watch tartan is Campbells

[Wompet]

Your just not as cool as us Campbells. ;)

This isn't what you are looking for but its interesting non the less
http://www.users.zetnet.co.uk/tartan/history.htm

Cool is overrated. I prefer to belong to a bunch of salt-of-the-earth folk who like to tear it up now and then.;)
(That may not fit all Robertsons, but it's a good description of my mother's ancestral line.)

Thanks for the link - paragraph 5 gives me a starting point at least.