The Folk of Haleth were nearly annihilated during the
First Age. They basically suffered a civil war after the deaths of
Turin and Brandir the Lame, whose rightful chieftainship Turin, his first cousin, usurped, when
Húrin arrived and the Folk of Haleth divided between the cruel and selfish chieftain Hardang and Manthor, who may well have been the rightful chieftain; the complete story of the ruin of the Haladin, who seem to have always been a fractious bunch, is told in
War of the Jewels, “The Wanderings of Húrin”. Few of them survived to emigrate to
Anadûnê.
The First House settled largely in western
Númenor. Like the small Second House, they were mostly dark-haired. The majority of the
Númenóreans, however, were from the Third House, who were mostly blond. We might well imagine that most of the Númenóreans were mostly blond-haired folk who strongly resembled the descendents of their kinsfolk who remained behind in
Middle-earth, the
Rohirrim of
the Third Age.
The Faithful Númenóreans in the second half of the
Second Age were mostly from the descendents of the First House, who were likely more dark-haired than blond, though by that time, the population was surely more mixed.
So if we follow this logic, the surviving Dúnedain in the northwest of Middle-earth were mostly dark-haired; but the bulk of the Númenóreans – and probably the surviving
Black Númenóreans of Middle-earth – were probably disproportionately blond.
Is it accurate? I don’t know. Does it fit what we’re given? I think so.
By the way, the nearest surviving relatives of the Folk of Haleth or Second House of the
Edain in the Third Age were the
Dunlendings, who used the epithet “Strawheads” for the Rohirrim. I believe the Dunlendings are described in the
Lord of the Rings and other writings of
Tolkien’s.