How can I print in monochrome on my colour printer? Not grayscale, but only pure black-white printing?
Quite simply, with modern printers, the idea of pure black and white printing is obsolete. Even where I have a black and white option on a printer (say a virtual PDF device, or my other printer), it really means greyscale.
Practically speaking your best option would be to tweak your source material to be black and white, then print that out