I'm trying to dig up the exact quote and source but I can not find it at the moment. At any rate...there is a reference in Clan Grant history where one of the pre-Culloden chiefs wanted Grants to be dressed in a tartan that was red and green... "broad-springed" or something like that was the term used. It certainly does not support a specific sett but a color preference for Clan members. But this is a bit of a middle ground between no clan association and specific adoptions of tartans by the clans. The Grants also adopted the Black Watch tartan very early because of the Clan's long association with the regiment.