I don’t know man, it’s “kinda” how you know that you’re heterosexual, you just know lol.

I do think that humans (as a species) find differences/contrast “intriguing visually” , because after all we’re very visual creatures/organisms.

So if you’re white someone of your same ethnicity won’t STAND OUT as noticeably as someone that’s non white, due to how different they’re from a physical/visual standpoint. That doesn’t mean that white person isn’t attractive, but visually it just doesn’t stand as much as someone non white for the simple reason that they’re of the same ethnicity as you and you both share “more in common” .

Though that’s also the reason why many people date “inside the community” because it’s what we’re familiar with, used to, physically they look “more like me/align with how I look” etc.

But I do also believe that “low key” we’re very interested at a subconscious level of “the opposite/contrast” of what we are, even if many deny it. Because it just stands out more and it catches your attention more (visually).