Concerning the offensiveness of the term, lets ask AHD:
PRONUNCIATION: nn-hwt, -wt
NOUN:A person who is not white.
OTHER FORMS:nonwhite —ADJECTIVE
USAGE NOTE:Many people object to the term <italics>nonwhite</italics> for referring to people by what they are not rather than what they are. Of course there are occasions, as when discussing an exclusionary policy such as the former system of apartheid in South Africa, when this emphasis is entirely appropriate. In many other cases, if it is relevant to mention race or skin color at all, a term such as <ilatilcs>person of color </italics> is often preferable to nonwhite. See Usage Note at color.http://www.bartleby.com/61/85/N0148500.html
The problem with all these terms is that people tend to remember the meanings of the words as they learned them in their youth. I seem to remember that "Farbige" in South Africa (20 odd years ago) were people with a somewhat skin but not actually black africans, e.g. indians, and that a number of different rules and regulations applied depending on a person's status as colored (Farbiger) or black (Schwarzer).
Since then, thank goodnes, a lot of things have changed. But, if you are not closely involved in discussions or processes about "race"-relations, you cannot keep up to date with the current shifts of meaning.
A few years ago as I was interpreting a panel discussion on transgender topics, I happened to translate the term "women of color" to "Farbige Frauen". The women of color present objected to the translation. When I asked, they said they would prefer to let the English term stand, i.e. People of Color, Women of Color should not be translated.
Ich würde nonwhite durchaus mit nicht-weiß übersetzen, eine usage note bezüglich der Bedenken gegen die Verwendung wäre wohl sinnvoll.