When Kaneki's hair turned from brown to white, was it because because of the stress ? Or maybe because of his change of heart. A lot of anime and manga use hair-colors to describe someones personality, so maybe it was symbolic like, his hair turned white because he admitted that he has to change his personality.. Does someone know the real reason or?
His hair turned white and nails turned black because of the physical and mental stress (the episodes in which Yamori tortured him)
It is mentioned @Wikia :
After being tortured by Yamori for a period of ten days, his hair became white and his nails turned black due to heavy stress, anxiety, and continuous bodily regeneration. This condition is known as Marie Antoinette syndrome. It is caused by extreme stress or emotional trauma like he had undergone. He also began wearing a form fitting black outfit when he had the intention of fighting as a ghoul, both for intimidation and practicality.