Do work in CMYK, that's for inking (is for light beams to use RGB).
If a vector graphic stays vector – as opposite to raster graphics image or 'bitmap' ("brought over" teachnically shouldn't be used) – you do not have a dpi issue, that will be resolved by the Xerox machine as its maximum.

I've tried one of those 'solid ink' printers from Xerox and the colour reproduction quality was horrendous. Black text was pretty bad as well. Be careful.

doesn't sound good, clauses. do you mean the colour of the print differed from that intended, or that it was just poor quality?

Thanks for the info,Alessandro. i thought that rgb was for computer printers and cmyk for 'professional' printers(again i dont know the technical term)
jonny.

rgb was for computer printers and cmyk for ’professional’ printers ...

To make it a bit more complicated ... Virtually every desktop printer also works internally with CMYK. However, because the printer mnf know most people cannot be bothered to learn color conversion (and use Word, which only has an RGB mode), the internal RIP is actually optimized for its own RGB-to-CMYK conversion. That depends on a lot of things, such as ink color (inks are never a pure color) and ink density. I have seen in practice that printing an image directly from Photoshop in CMYK mode gave a poorer result than the same image in RGB mode. That's just because the printer internal conversion is better than Photoshop's.

Perhaps you should just try, and bet on RGB first, as that probably comes out better than CMYK.