There is a apparently an issue that has not received too much attention.
Apparently on HP Laserjet printers like the model CP1215 even when you set the printer to only use black toner the other color toner is still being depleted. So you may only be printing black & white pages, but after a so many pages you will be out of color toner. Which is quite a shock to many users if you are not printing color.
So buyer beware with the HP Color Printers that this can happen.
I am not sure what other models are affected, but I know that other printers appear to behaving in a like manner.
Also, even if you have plenty of black toner but you are out of any color, you will not be able to print. So be prepared and check your pages remaining periodically. Or you may find yourself not being able to print.

Note to HP: Please consider fixing this, it appears that it is a ploy to make users consume toner, even though they are not using it. Perhaps a explanation why this has to be this way?