Well the definition of "black" includes many African ethnic groups just like "White" includes European ethnic groups.
Make sense why? Because she's suppose to be Egyptian or whatever? they have found mummies with what appears to be light hair and pale skin and I've seen hieroglyphs of people with near white looking skin.
the dna mummies that they tested show that they have the greatest resemblance for people from the Arabian Peninsula and have a much a greater resemblance for people from certain parts of Europe than Sub-Saharan Africa. So take that as you will. Artemis being pale with red hair and green eyes makes just as much sense to if she looked more Mediterranean looking.
"Caucasian" aka the "true" term for "white" people encompasses many ethnic groups going from Europe, North Africa and South Asia and West Asia (aka Middle East). EDIT: the "White" race is a silly concept itself. "Caucasian" people are from more than just Europe and like you said there are European ethnic groups, especially in Mediterranean Europe that have brown skin and "exotic" features but are still "white" and many "Non white" ethnic groups can have very "ghost white" skin but still not be "seen" as "white".
America and several other countries in North and South America recognize Arabs along with Europeans as "white". And they are diverse as any other ethnicity and can be ghost pale to dark brown, have blonde, brown or red hair or blue/green/etc eyes, etc just like Europeans. Though as race is an arbitrary concept, some people only consider anyone of European and just European ancestry to be "white". While others view anyone with pale skin as "white" regardless of their ethnic background.
There was a huge debate on whether Gal was a "white" person or not shortly after Wonder Woman was released. The general conensus was that she's "white" and that her being from Israel or Ashkenazi Jewish doesn't change that. Which is funny because, Gal has "browner" skin than other people I've known who known who don't see themselves as "white" and In Gal Gadot's case, An Israeli person there claimed that where he's from in Israel, they don't see "race", like America does they just see Ethnicity. Example - He claimed that while Gal, an Ashkenazi Jew is seen as "white" in America, she's just Ashkenazi in Israel because that is her ethnic origins.
True. I've also met people who due to their ethnic background aren't seen as "white" in America or to many other people that they met but call themselves "white" regardless because of their skin tone.
I also know people who would much rather identify with their ethnicity instead as opposed to "race".