Board Thread:Lore Discussion/@comment-96.33.33.144-20160604103039/@comment-28157605-20160608050119

Hard to say, most of the Altmers in Skyrim are mages which means they wear a hood. We have Faralda from the College of Winterhold, for me she have brown hair. Linwe, a thief from the Summerset Shadows guild have dark facial hair so I supposed he's brown too (I've never really paid attention despite doing the quest many times).

You can also do a dark-haired Altmer yourself.

I don't think it's genetically impossible (no 'fake color' excuse) and in real life, the concept of 'ethnic purity' is not possible. Since Altmers can reproduce with other races, the father just have to be dark-haired. The child take the mother's race but sometimes also take features from the father's race.