The dark elves (Moriquendi, or Avari) were called that because they hadn't seen the light of the trees of valinor, not cause of the colour of their skin. The colourblind casting is both stupid as it doesn't have any internal logic like they have in House of the Dragon and goes against canon. However, the real problem with the show isn't this ir the fact that they are butchering the lore but the awfulness of the writing. It's just really idiotic and badly executed.