ciao marco
- don't use the print preview (except you know you need the features it provides... which is not the preview of the way your document will be printed).
- for the preview use "view > preview mode" instead.
- you will get a real preview by producing a pdf and looking at it with a good pdf viewer (if possible, the same one you will be using for printing).
this having been said:
- how are you setting the background color?
ciao
a.l.e