Hair color is something you're born with and is a genetic mutation based off lineage and other factors. I don't think they directly corelate and it wouldn't necessarily even make it to the Supreme Court. Most businesses aren't going to appeal to say that they can discriminate based on hair color nor willingly admit to doing so, nor would they ever likely make the argument that they did it and that it is okay.

The law doesn’t say “things you are born with”, though. That’s a common theme with the specific categories it does name, but only those specific categories are protected.

It isn't specifically limited to those specific narrow words by the most limited means you're thinking. I'm sure they could make that argument, but only a fool would risk a discrimination lawsuit based on hair color. Even if that is the specific reason a person would have to be either a fool or want to try to challenge the law, and there is no guarantee after losing that the Supreme Court would even take the case. I don't think the Supreme Court would even want to touch such a case nor that it would be ruled on in the manner you're thinking.