From The Heretic Knowledge Vault
They might have made things easier and just called themselves High Elves, but no, they were too fancy for that.
In cooperation with the Keiren they also seem to have cornered the market on red hair (according to Poe; see below).
(Taken from this thread in the Forum)
Destichado wrote: Sarine is a Highland Elf. We've established this -iirc, Poe came by and wrote something that all but said it outright.
(Also from the same thread:) Red hair is unique to the Sanguen and Keiren.