Perhaps in the fanfic, Naruto is trying to fit into a different group or culture. His original hair style might make him stand out in a negative way in that context, so he changes it to be more accepted. Or it could be part of a bet or a challenge. For instance, he loses a bet with his friends and as a consequence, he has to change his hair style.
One possible reason could be some sort of new chakra transformation. Maybe he taps into a different power source that affects his physical appearance, including his hair color. For example, if he were to inherit a special kekkei genkai from an unknown lineage that has the side - effect of changing hair color when activated.
It could be due to a genetic mutation in the Naruto universe. In some fanfictions, there might be a hidden genetic factor in his family line that gets activated. For example, perhaps Minato or Kushina had a recessive gene for white hair that Naruto inherits and it suddenly shows up under certain circumstances, like extreme stress or a coming - of - age moment in his ninja journey.
One reason could be that Naruto wants to give a fresh take on the story. Maybe he feels the original fanfic doesn't do justice to the characters or the plot. Another reason might be to attract more readers. If the fanfic has become a bit stale or predictable, changing it can bring in new fans.
Well, perhaps it's a sign of his connection to a new, mysterious entity. For example, he might have made a pact with a powerful ice - based spirit or demon, and as a result, his hair turned white like snow. Or it could be due to a powerful transformation that was caused by a unique combination of his Uzumaki and Namikaze bloodlines. In the world of fanfiction, there are countless ways to explain such a change, and this is just the tip of the iceberg.
In terms of his relationship with the villagers, those who once bullied him for being an orphan and having a different look (with his blond hair) might be even more hostile if his red hair makes him stand out more. However, there could also be some villagers who see his red hair as a sign of something special and start to respect him more, which could lead to a shift in how Naruto views the village and his place in it.
One possible reason could be extreme stress or trauma. In the Naruto universe, he has faced many difficult situations. If a fanfic writer wants to show the toll it takes on him, white hair could symbolize that. For example, if he loses someone very close to him like Sasuke in a more permanent way, it might be so devastating that it causes this physical change.
Maybe he wants to rebel against his family's traditional image. In the wizarding world, the Malfoy family has a certain 'pure - blood' and proper image. Dyeing his hair could be a way for Draco to show his individuality and break free from the constraints his family has put on him.
Maybe he wants to change his look to disguise himself from his enemies. In fanfiction, there could be all sorts of threats and he might think a new hair color would help him blend in or not be recognized so easily.
In some fanfics, Naruto might leave his family because of a dangerous threat approaching them. He could believe that by leaving, he would draw the danger away and keep his family safe.
If he changes his hair to something more subdued, it might show that he's becoming more mature. For example, if he goes from his spiky blond hair to a shorter, darker style, it could symbolize that he's leaving behind his wild and carefree days.