Uh, he’s not an elf or human at all, he’s a dragon pretending to be a mortal. Again, show me a half elf/human with bright blue hair that isn’t a dragon in disguise.
Every dragon doesn’t show their draconic attributes the same way. Some hide them fully, others make it known. Ebonhorne is an example of the former, since he wanted to blend in with the Tauren who protected him. Onyxia is another example, since she used her visage form for infiltration into the higher levels of Stormwind nobility.
Wrathion in an example of the latter, since he is proud of his heritage and wants to openly display it via burning red eyes.
They’re all Black dragons.
You seem to not understand that dragons take visage forms for different reasons, and thus have different ways of showing, or not showing their draconic background. Your inability to show any half elves/humans with hair like Kalecgos is another example of a dragon showing off their true nature while in visage form.