Well, not really. Most Brazilians don't have that color. It's only a few that have, and they're called "negros" (or "negras" for women, in Portuguese). It's not racist by the way. It's just a name for the color of the skin: Branco (white) and Negro ("black", is that how you call it in english?). In some parts of the country there are more people with this skin color, but in all places I have lived here I there have been very few people with it. Almost all of my friends (women) where I currently live don't have that skin color.
But it should fit for a joke, though, because it seems everyone outside South America (or even just outside of Brazil) think all Brazilians have that skin color, specially women.
Preto(spelling?) is black.
Unless of course theres black as in colour and then black as in skin colour?
Im not too sure, my parents dont really tell me these things.
Refering to someone as "Preto" would be considered racist in Brazil, since it should only be used to define the black color instead of the black skin color which is "Negro". Spelling is correct though.