Check to see if the problem is hardware or software related.
Print off a demo page from the printer itself. If there is a problem here then you will have to look at your cartridges.
Next test is to pritn off a demo page from your OS. Windows has a test page that you can fire off from the Pritners and Faxes window. If there are problems here then perhaps there is a driver conflict and you should uninstall and reinstall.
Last test is to print off color documents from multiple applications and file types. Problem here suggest a configuration conflict on that particular application.