I think someone can be culturally X, legally X, ethnically X, etc. for any country X. I have met people from European backgrounds who grew up solely in Japan and would consider themselves Japanese, though some often wrestle with issues, both internal and external, around that since they eyes of someone seeing them almost always see only "other" first. They hold Japanese nationality, are culturally Japanese, but not ethnically Japanese. Then again, ethnicity is its own thing as well.
It's a complicated topic and I'm certainly no expert on it. I'm a white guy of mixed western european ancestry who grew up in a town where that was the majority (and had no shortage of anti-Semites and racists, as I would find out as I got older). I've just been trying to learn along the way. I've been living in Japan for the past decade and see some of the small things that cause extra hurdles for those of foreign backgrounds (ignoring outright racism in that; just little things that only work for people whose names are <= 8 characters, require documentation only Japanese people can ever get, etc.) People who don't know me will often just use one of the words for foreigner or outsider and clarify with white person if that's ever necessary.
I guess I have a question: If you found a child with "darker skin shades" who was lost and you needed to create the most accurate description possible to the police over the phone to help them, what would you use to describe them (until the police would arrive and obviously see with their own eyes)? I think I would personally pick the closest colors for everything I could and not care about any sense of political correctness.
There have been attempts in the US (and probably elsewhere) to replace "black" with "African American" or other similar things. Ask an American Indian what they want to be called. Some would say "Native American" though others reject that because they are older than any conception of America and are not native to that nation. Others will be OK with "first peoples/nations" (often used in Canada, I think), "aboriginal", or just "Indian" since that is the term they grew up with.
A bit of humor to close off with: sometimes people from the US will travel to the UK or elsewhere and, rather than using black to describe just the skintone of the person, will say "African American"... to people who often have never set foot there and certainly aren't citizens.