My former wife is native Venezuelan and I met her while we were both in graduate school in New York City in the 70's. We would watch American TV and I would have to explain the culturally-based humor of American comedy shows like Saturday Night Live.
One other thing puzzled her. We'd watch Harry Belafonte perform and she'd ask "Is he Black?" We'd watch Lena Horne perform and she'd ask "Is she Black?" In her native Venezuela, Belafonte and Horne were not considered to be Black. They were just like everybody else. Her confusion made me realize how indoctrinated I was by my culture's imaginary racial distinctions.
I noticed a "difference" because I have been taught to notice a difference. We all have been taught to notice a difference. We are all racists. Some of us are just aware of how contrived and ridiculous that indoctrination has been and how we must strive to overcome it.