No Color Printing.

I have 2 different clients, one with a Zerox Docuprint 750 and another with an HP DeslJet 720C, with the same problem : Both are loaded with quite new Color Cartridges, both have reinstalled Newest Drivers, and Set Up to Color printing, and Both areprinting only Black and White .They areworking with Win98 SE Hebrew, Office 2000 or 97 . Can anyone help me out ? I am doing something wrong ? – Arie – .