Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
If the drivers, as distributed by HP on either an HP-branded CD that came with the printer(s), or else as distributed on HP's website, were installed properly, there might be an option in the printer's driver settings for 'Grayscale' printing.
But I suspect this may not be quite what you mean in your question. Do you mean, a way of switching to using only black ink for *all* printing? and back again to full color?
Though some printers by some manufacturers may switch to using full-color inks in a mix to produce black when the black cartridge's ink has run out, it is not a switch you can activate. Except perhaps by the 'Grayscale' option, in the printer's driver settings, when such an option is provided.
That's puzzling! but are you sure you are selecting Grayscale for the printer you have, rather than for another printer, or for a printer you formerly had but have not uninstalled from your computer, etc. ?
Is your computer a Windows PC, or an Apple computer ?