the indigenous european substrate that we know of mostly had to do with maritime words - words for things like sea, boat and fish. we don't know a lot about them, but they seem to have been maritime-oriented. that's not surprising. from the dawn of history, the time of the sea peoples, to the viking invasions of europe, about all that settled civilization knew about the north men was that they lived in their boats. these immigrants came from the land of ice and snow, on their boats, and they were always mean when they got to the south. that trait is older than the aryan invasion and something that withstood it.

the genetic traits of northern europe would have been connected to an anatolian farming group that was caucasian but not yamnaya, not aryan, and also to a remnant post ice age hunter-gatherer population. the farming group would have come from the caucusus mountains, through armenia, through turkey and spread widely across europe. were they basque-speaking? there is a theory that the basque languages are related to kartvelian languages, and tying the farming expansion genetically to the kartvelian language would make some sense of that, but i don't think that's broadly accepted. not yet. unfortunately, the perception is that they may have been middle eastern in origin because that's what the bible says, and it is what the bible says, but it's not actually what the genetics say. my own opinion is that the obvious is in front of us - they were kartvelians and the basque language is the last trace of them. (the basques overwhelmingly have genetic steppe ancestry like everybody else in europe). i also think the sumerians were a part of this same lineage, and of kartvelian ancestry. on that point, it's worth pointing out that the sumerians were known for their black hair, in their own writings.

the yamnaya themselves came from somewhere around the caucusus but moved north rather than south. this is shortly after the last age, and some kind of flood mythology actually fits the evidence fairly well.

the reality is that we know that nobody had blue eyes at this time because the mutation is more recent than this, but all three groups (yamnaya, proto-basques-kartvelians and european hunter gatherers) would have been different shades of white and the lighter hair was probably already there when the farmers got there, too.

blonde hair has survived multiple population overturns because it is strongly sexually selected for. it is not a trait of dominance.