Hey, they had a great sense of style. :^) Thanks Bodleian_Girl.
The Scots were entirely Irish, but entered a Caledonia (which is now Scotland) already populated by the original Blue Devils (Picts). It's not surprising that in the intervening 13 centuries there would be some variance. The Scandinavian DNA many western European ancestry folks in America find in their tests comes from, not surprisingly, the Vikings, who entered Caledonia before the Scots did, and were already swarming all over Ireland, Shetlands, Orkneys, etc quite early. I'd not be surprised to learn that the Vikings helped crush the seagoing trade between the British Isles and the eastern Roman Empire, known to have gone on in the "Dark Ages", between the Roman exit from Britain (let's call it Rexit) and the Anglo-Saxon takeover of the British interior. The Vikings also carved out Northumbria, and forcibly settled a big chunk of that Anglish territory in the very same interior.