Native Brazilians had a darker skin tone and most of them stil have a darker skin tone. I don't think the first person that would come to your mind when thinking about brazil would be a white person with blond hair, right?
Every country has immigrants, but if you think about africa you think about black people, if you think about russia you think about white people, but they all have different ethnic groups.
Luffy looks more japanese/asian than brazilian imo.
Zoro is japanese because he has alot of japanese related things, like Katanas, his belly warmer thing lol, trained in a Dojo etc. etc. - but he doesn't look like the typical japanese person. Or would you think he was japanese without his katanas and belly warmers?