You need to get into Printer Preferences, where you can select black/grayscale from the Print Options list. Following this link:
will take you directly to a manual in pdf format which you can save to your computer for future reference. The section you want starts on page 49 and on page 50, there is a screen shot of the properties you need to get to on the computer, to put a tick in the "Black/Grayscale" box.
Hope this is helpful, if so would you please register that with Fixya