Fiat's Nero

I heard on John McElroy's automotive news show, Autoline Detroit, that Fiat will use Italian names for its colors in its marketing and ordering materials.  For example, red will be called rosso and black will be nero.  (Que Rome burning jokes) What I don't understand then is why Fiat is calling the 500 "Five Hundred" and not "Cinquecento", which is its proper Italian name.  Some Americans many