His hair probably turned white while he stayed at the rift. It may be due to corruption or something.
kind of!!
spoiler:
in the rift there was this thing called "the whitening" which caused people to turn into white monsters once consumed this white dust/thing.
euijae and his comrades in desperation started eating the mutated monsters (which were other people, i think if i remember correctly.) who mutated.
euijae only ate one mutated monster before finding out it was a mutated person, after that he stuck to drinking the dirty water in the rift while his other comrades ate the mutated monsters and mutated themselves too.
So yeah, thats pretty much the reason his hair's white, hes going thru the "whitening"











Dane your soooo HOT! I'D BUY YOUR CALENDAR ANYTIME, EVERY YEARRR