[jallanite]

Fëanor’s three (not two) red-headed sons (Maedhros, Amrod, and Amras) and their mother’s family may have had darkish red hair, in which case there is no contradiction to Tolkien’s rule that among the Noldor their locks were dark save in the golden house of Finrod.

Glorfindel is more of a problem. One can speculate that Glorfindel had a mother of the Vanyar, possibly sister or other close relative of the Vanyarin Elf Amarië who married Finrod. If so, Glorfindel could be loosely reckoned as belonging to the golden house of Finrod. No pure-bred Vanyar joined the host of the Noldor on their return to Middle-earth, in which case Glorfindel’s closest relatives in Middle-earth would probably be Finrod’s sons.

Most of the folk of Lórien were of Silvan origin. The Silvan Elves of Lórien were mainly of Nandorin descent but also mixed with Avari and Sindar. Presumably this golden-haired elf of Lórien would be of Avari origin from outside the “People of the Great Journey/People of the Stars” about whom Tolkien is writing when he discusses hair colour.

There is also Celegorm the Fair, one of the sons of Finrod.

Considering that Tolkien later decided that the Silmarillion and associated tales were to be understood as somewhat garbled Mannish tradition, perhaps indeed we must understand that the tradition that Tolkien presents about dark-haired Noldor has been over-regularized. The Noldor were only mostly dark-haired.