HP Deskjet 6600 series printer - (Windows) Reference Guide

Gray photo print cartridge
The gray photo print cartridge, used in conjunction with the
tri-color print cartridge, prints high-quality black-and-white
photographs.
The gray photo print cartridge can be purchased separately if
it is not included with your product.
Installing the gray photo print cartridge
To install the gray photo print cartridge, remove the black
print cartridge from the printer, and then install the gray
photo print cartridge in the compartment on the right of the
print cartridge cradle.
For more information, see the print cartridge installation
page.
Using the gray photo print cartridge
To use the gray photo print cartridge, follow the steps to
print a black-and-white photo.
Storing the gray photo print cartridge
To maintain the health of the print cartridge, follow the print
cartridge storage guidelines.