Hello and from South Carolina.

Are you referring to one of the tartans with a white background? These are usually worn by Highland dancers. If I recall correctly, the MacGregor clan chief has approved the green-on-white version for clan members who dance.

Otherwise, the chief is rather a minimalist regarding tartans. His approval extends to the "red and green" (the usual version) and the "red and black" for clan members.

There is more at the Clan Gregor Web site, here.