@Kaarme Since it's not actually in color, it could be that the ones with darker hair here all have very dark shades of other colors but none of them actually have straight up black hair like he does? A lot of characters with dark brown hair probably end up looking like their hair is black on pages like these. You probably see that happen often with the lighter ones too, like you might assume a character is blonde until you see a color page and they were apparently white or silver haired. Or perhaps theirs are how black hair normally appears in this world, and something about his stands out somehow that they didn't express adequately. Extra glossy or something.
I'll just leave it at that, I feel like I'm going on a little too long about this and I apologize if you feel that way too.
@Glomoro No, it's okay, it was just a little joke, knowing in B/W manga there can only be white, gray, or black hair, so it's all in the speech. It's just funny in the same way as the police looking for a man about 30 years old with short black hair in East Asia. Quite a few of those around.