People are categorized in that manner every day. Perhaps you're trying to say that's regrettable and inaccurate?
> To identify even yourself as belonging to a distinct "color" is just a fabrication of American culture
Certainly, but it's a culture which still exists. It doesn't go away just because you announce that it's illogical and unfortunate. I think you may be falling prey to the is-ought problem[1].
(To be clear, I'm not expressing a view on Github's actions, but I think it's somewhat naive to suggest that there aren't real problems out there.)