The word "gringo"

The word "gringo", according to "Urban dicitionary":
"Folklore says it was generated when the US invaded mexico, wearing green uniforms, and the people shouted at them "Green Go Home". 
With time it lost all derogatory status and was turned into the most common word to refer to any US citizen."
In Brazil, this term is widely used and a foreigner from any country can be called "gringo" (male) or "gringa" (female), not only US citizens.
When my friend Greg Lehman, from Minneapolis, USA, was in Brazil, two years ago, he was called "gringo" all the time. 
Brazilians like to use this word for all foreigners because it sounds a little funny but it is not pejorative.