Those would fall under cultural appropriation, right? (pretty sure I know the answer to this). Every year on Nov. 1st I do a sugar skull costume, and this year I was thinking of doing a Frida Kahlo skull (with one glorious eyebrow). I was just thinking about it, and that'z probably not ok, huh?
Some googling found a very small amount of talk about this, but that doesn't mean it doesn't count.
On a side note, Mexican folk art is having a moment; I've always loved it but never felt comfortable producing any. It's just beautiful, though.
Update: Duhh. Of course it is.
Update 2: Maybe I might dress just as Frida Kahlo, minus sugar skull. Not because of Mexican stuff, but because I got real attached to the idea (I usually portray an artist every year). NOTE: this will involve no pigmentation of my skin! What do we think about that?