Its such a common thing that a character having blond hair is supposed to be visual storytelling to fill you in about a character's personality and backstory in a lot of works. They are either a rebel/delinquent, or a foreigner (and always at least partially Japanese because otherwise that's a big problem for them).

This doesn't always apply in series with rainbow colors present, but even then the blond specifically often will still get singled out as a big deal because of how much cultural baggage the Japs have with it.