To print successfully from a Mac running OS X it needs to be setup using Print Center. This allows the Mac to know the capabilities of the printer, if this is not set it will be asumed that the printer is a basic black and white A4 model (generic postscript printer).
Open print centre then select Show Printer List from the Printers menu.

Click on the printer you need to setup in the printer list and select Show Info form the Printers menu.

Choose Printer Model from the drop down menu of the dialog box that appears. A list of network printers and their details is available here.

Select the manufacturer of the printer from the drop down menu.

Select the model of the printer from the list and click on the Apply Changes button.

The exact configuration of the printer can be set in the Installable Options section of the Show info dialog.

The printer is now setup for use with your Mac.