Western beauty standards are pervasive yet don’t always have a strong grip on other cultures. While there is a frankly disturbing correlation between youth and beauty in most places, the way it’s expressed is varying. In the Philippines and perhaps throughout Asia, pure black hair not only connotes youthful beauty but also goes hand in hand with fair skin.
At least if it’s not too pale to the point where if you either have vitiligo or albinism you get stared at often, sometimes accompanied by unkind remarks and sneering. I guess among Westerners, it would be blond hair as hair darkens. There are adults that stay blond or at least light-haired enough throughout adulthood, thus seemingly younger.
They are however not any less naive or stupid. One study suggested that they might even be smarter than average. One shouldn’t be surprised if there are naturally blond people that don’t fit these stereotypes in any manner. And could simply be aberrant in other places especially if the average population is dark-haired.
That beauty standards are fickle throughout time and place.