Hi...actually the answer to this problem is in the Xerox Online Support Assistant here on Xerox.com. Here is the link to the Phaser 8560 Knowledge base.
Just type in, "set default color" in the search field for the knowledge base and you will find your answer (essentially there is a setting in the print driver if you are using a MS Windows based driver...the knowledge base article contains step by step instructions as well as color pictures to resolve the problem).
Hopefully this helps to resolve your problem. If not, at the top of the knowledge base window you will find the 800 number for contacting the Xerox Customer Support Center (800-835-6100).
My Phaser 8560 shows that it is out of yellow ink although I can see one yellow ink still inside waiting to be used. My first question is whether there is a way to override this setting so I can continue to print until my new inks arrive in the mail? Alternatively, the info screen says I can continue to print in black only, but when I go to a program such as Word and try to print out a black and white page I still get the out of yellow ink message. How can I print successfully in black ink only?