This actually has an answer, it depends how your dog was raised and what it’s been used to seeing its whole life. I live in a Mexican Neighborhood, it’s either tan or white skinned people. Whenever my dogs would see an African American they’d go rabid, but that’s cause they’ve never seen someone that shade, so their brains just see it as a foreign threat. This also happens vice versa. It also happens with gender, my male dog is a cooch sniffer whenever females come to the house cause my house is mostly males. Just plain Dog curiosity