The source for the above is Sword Coast Adventurer's Guide for 5e + Races of Faerun for 3/3.5 plus in the case of "Dark Elves" just my observations from lady penitent
Mmh! I do find it curious the large masses of people claiming that elves are 'white and blonde' and 'too caucasic'. Then you read the descriptions and you find out that the vast majority of them aren not actually white and blonde. There are so many possible combinations, from blues and green hues to very dark skin. Wood elves per instance are said to be the most populous of elves, and they're tan, and dark haired mostly.
On your thoughts about giving subraces ethnic hints, a random thought that occured to me was this elven depiction of 5e Player's Handbook:
She has the classic angular features, but also... Do I have a big imagination, or she kind of looks like Rihanna? :'D This is an excellent example of an ethnic looking elf, in my opinion.