I just learned (slow on pop culture pickup) that Jennifer Anniston is Greek, with ancestry from Crete. So it looks like some of those Vikings hit Crete!
The Irish-American family my mother grew up in had 12 children with diverse genes. Some very light blonde, others almost raven-haired; some tall, some short. ALL, tho, had very fair skin and very blue eyes. Beyond that, it was some crazy mix.
It has been said, though, that a lot of Greeks are actually descended from Slavs and Albanians and others who pushed down the Balkans into Greece.
Just like a lot of Turks are descended from Greeks and Armenians who went over to Islam.