By "cuturally determined" visual clues that are used to determine a person's racial category I mean that those physical descriptors that the culture determines are the ones that fit a particular race.

In the United States, for instance, there are African Americans who have white skin color, blue eyes and blond hair. These people may be of first generation of mixed racial ancestry {meaning one Black birth parent who is Black, and one birth parent who is non-Black}.Or they could have two birth parents who are Black, one or both of which being very fair skinned.

There are soooo many gradations of African American skin complexion and hair texture, and facial features {nose, lips}. However, this culture has established a profile of what a Black person looks like-
light to dark brown skinned, broad nose and full lips, tightly curled hair in its natural state-this is what I mean by visual clues.

Sometimes people can't figure out "what a person is" using those visual clues. That's what I mean by persons who are of ambiguous ethnicity.

And Dianavan, it is my view that the definition of who is or is not Black or White in the United States is a racist construct in and of itself. If a person who is 'half Black and half White", wanted to say that he or she was White, and that person "looked Black", would he or she be accepted as White?

I don't think so.