That is actually a true phenomena when a person's hair might lose all of its color, and turn into white/grey, from a huge amount of stress, or some sort of similar mental damage (regardless of age, so could happen to a young person too)..
Though hard to say if author actually thought it so far, or was it just something to mark his change of being, and an add to that "cool" factor since he's basically (at least) a demigod compared to normal ppl.
Also, thanks for the 1st chapter.👍
This looks promising and definitely gonna read the future chapters.