Talking about the word Negro, sometimes depends the context:
Ex:
1- There is one dancer in tv, everbody call him Negro Luengo (surname), he is white, with black hair like the italians, and that isn´t an offense.
2- When the people is angry with someone, but very angry, sometimes use the expression: Que negro de Mie***, that is offensive.
3- When somebody does one joke with a dark humor, you can say: Que negro que sos! and that is beetween friends, laughing with complicity.
4- You go to the Beach, you can back to your work and everbody can call you, Volviste, estas re-Negro? You came back? You are very Negro!
5- Sometimes (this happens in my bar), there is many people talking about many things, and there is one or many tan people or dark skins, and someone says: He cheats to his boss, and hi doesnt show up in his work, ´cause he was sick?? Nooo, he was lying, and say: Que negro pata sucia, el chanta! (What a Negro Dirty Foot, the cheater!) and they apologies to the tan people, saying: I mean, not a Negro in the skin, I mean Negro from the soul (negro del alma, people with bad intentions), that is offensive, but they explain that.
5- My friends calls me Negro or Negrito, negrito lindo, negrito monono, and that is not offensive for me, they are saying that with truly affection.
Well, there ways and ways to say and use Negro.
"Una cosa es una cosa, y otra cosa es otra cosa" (slang)
I almost say that famous joke about: No es lo mismo un metro de encaje Negro...
Bye, Vick