Kilt outfit

[OC Richard]

You're right, numerous 18th century portraits show the free mixing of tartans.

There wasn't a concept of "clan tartans" then.

Yes in the 18th century there were commercial weavers like Wilsons of Bannockburn weaving stock tartans so certainly you could order a large quantity and make a whole matching outfit, and these were indeed popular.

But you also see people mixing tartans, here in the mid-18th century mixing three:



I put together this collage showing mixing of tartans from the mid-18th century, the 20th century, and currently in the military