Of course Blue Eyes would not be the only criteria for selection, the person would have to offer pretty much the same things as today, strength, security, social standing, appearance and so on.
And as the mutation that caused Blue Eyes does not appear to have brought any debilitating effects along with it, the Blue Eyed individual had to rely on the rest of his genetic hodgepodge and what he made of himself to put those things forward...
But Blue Eyes may very well have been an advantage to an individual who offered all those other things a mate looked for, over others who were not Blue eyed.
The high number of Blue eyed people in Iceland now, points to Blue eyed individuals being in the majority in the first settlers, so perhaps in the majority in the places they emigrated from,,,and something had to be the defining trait that led to them successfully procreating more than non blue eyed people...History shows the vikings were a hardy lot on average, they had much to offer, so how did most of those who went to Iceland (theoretically) end up being Blue Eyed. (of course the near population crash after settlement could be the reason Blue Eyes prevail,,)
Just conjecture on my part, and I am no longer Blue eyed, they went brown at three.
SeerBlue