Is there a measure of "blackness" (or "whiteness" or "asianess" or "whateverness"), or is it decided ad hoc by the committee that provides the scholarship (as a

Is there a measure of "blackness" (or "whiteness" or "asianess" or "whateverness"), or is it decided ad hoc by the committee that provides the scholarship (as an example)? I am not sure how discriminating some people as "minority-enough" can be legal (except if there are some genetic tests I guess)