To default the machine to printing black iand white you must change the default color in the driver. Please take a look at this solutiion in the knowledgebase for your machine. http://www.support.xerox.com/support/8500_8550/support/en_US.html?objGUID=6010
I hope this helps.
To keep costs down I would like to print in only Black ink, without haveing to feed the machine color ink for no reason. Xerox 8550. Is this possible?