Same as anyone, tbh.

Identity is internal, always.

The only question is if you can get anyone else to go along with it. If you’re Irish, pale and otherwise unremarkable, good luck convincing anyone you’re black, much less a specific African ethnicity, you dig?

For folks that are multiethnic, there’s a different challenge. It isn’t so much that, depending on what ethnicities are involved, you can’t get people to agree at all, it’s that some combinations are rejected by both/all of those groups, or have trouble with their identity not fully matching the culture of those ethnicities.

That’s true even when the two groups are the same “race”.

There’s also the ugly truth that in many parts of the world (not just places once colonized my Europeans and/or part of the slave trade) there’s a one drop mentality still in place.

Here in the states? You’ll be up against it if you have any African ancestry that shows. Even if you just look dark enough for someone to assume that heritage, you’ll get pegged as black, and good luck with it since it doesn’t really matter what race the other person is, they’ll have an opinion on what you “really” are.

It’s bullshit, but the world just hasn’t moved past it yet.

So, when it comes to your self, your inner being, it’s more useful to identify as whatever your culture is than race or even ethnicity, when you’re multiethnic. Just don’t play the game at all, reject the bullshit and build your self based on more reliable factors.

If you want to partake in the racial cultures your appearance and heritage match, go for it. Chances are you’ll have hassles with any/all of them, but it won’t be all the time.

Lemme give am example.

My sister in law has a dad that’s very dark skinned, and is a descendant of slaves. Recently enough that his grandmother was a slave. Her mom is descended from german immigrants that came over sometime in the late 1700s or early 1800 (the dates in family bibles contradict). So, her mom is white, and was raised with a good bit of the German immigrant culture.

She identifies as multiethnic. She embraces both known heritages and their associated cultures. She doesn’t feel the need to pick one. And she’ll fight over it too. She has fought over it. My favorite quote of hers is “I’m fucking American, deal with it”. And she’s so fucking right :)

Now, compare that to one of my cousins. Dad is the same mix of German, Irish, and miscellaneous European descent that I am. Mom is black, light skinned, and embraces black american cultures. My cousin says he’s black, but also accepts and enjoys the other parts of his heritage.

There’s no single answer for you. You are, identity wise, whatever you’re willing to claim and enforce. If you’re dark skinned, you’ll have a harder fight enforcing that you’re “white”, no matter how much of your ancestry is from people with pale skin. But you can enforce it, and make that identity work. But, if you’re very dark skinned and lay claim to (as an example) whatever polish heritage you have and say you’re polish, you’ll likely have less fighting to do.

If you’re more asking what boxes you check on forms, it really is about skin color more often than not, here in the states, and in some other places from what I’ve heard.