Shikamaru might just sigh and say something like 'What a troublesome thing to do, Naruto.' But deep down, he would also be a bit curious about why Naruto decided to dye his hair red.
At first, Naruto might be really confused. He's used to thinking of his friends as his support system, so when they turn on him, he doesn't understand why. He'll probably try to talk to them, to ask what he did wrong. If they don't listen, he could become really sad and withdrawn. Maybe he'll start training even harder, using the pain of being rejected by his friends as motivation to become stronger.
Ash could respond in different ways. He might try to confront his friends immediately to get an explanation. If the betrayal is really bad, he could cut them off completely and focus on his own goals, like becoming a better Pokémon trainer. He would also probably have some internal struggles, as he has memories and experiences with these friends that he can't just forget.
He might be extremely hurt. Harry could go into a state of shock and disbelief at first. He may isolate himself, not wanting to trust anyone else for a while.
Naruto might initially be shocked or confused. For example, if they prank him with the fake ramen, he'd probably make a really funny face when he takes the first bite. But then he'd probably laugh it off because he has a good sense of humor.
He might initially be in shock and disbelief. Naruto has always valued his friends highly, so it would be a huge blow to him. He could try to reason with them at first, asking them why they are doing this.
Some of his friends were probably shocked at first. But then they might have become curious.
If his friends continue to ignore him, Harry could become sad and withdrawn himself. He might start to isolate more, spending time alone in places like the Forbidden Forest or an empty classroom. He might also lose his confidence in himself, thinking that he is not worthy of their friendship. In his loneliness, he could focus more on his studies or some solitary magical pursuits, trying to distract himself from the pain of being ignored.
His friends might be shocked at first, but then start to really enjoy reading it and discussing the ideas in it.
He would be heartbroken. Naruto values friendship above almost everything. At first, he might not believe it and try to reason with his friends.
Maybe he just wants a new look. Naruto is always known for his wild and adventurous spirit, so dyeing his hair red could be a way to show his rebellious side or simply to stand out more.