So boring to see these lame tropes that all dark-haired girls are insecure social outcasts and all blonde girls are popular and confident pop up in every manga. Is every mangaka living in some cheesy comedy form the seventies?
@Pachka84 tbf in Japan the only way to get blond hair is to dye it, so usually those who dye their hair are the ones who care about their appearances or who want to rebel so they tend to have stronger personalities or resolves.
Or they would be foreign, and the stereotype over there is that foreigners especially of the western kind are louder and less reserved. So it's very much rooted in cultural stereotypes.