Hewlett-Packard printers use process color inks (cyan, magenta, yellow, black, and on some machines, light cyan and light magenta) to print color images. The gamut of colors that these inks can print is different from that of a computer monitor. It is also different from the gamut possible with many spot colors and Pantone® spot color inks.
A special function in most Hewlett-Packard printers, called Automatic Pantone Calibration, will substitute colors outside the gamut of CMYK inks to print named Pantone spot colors when they are encountered in the print data stream. This Automatic Pantone Calibration function allows these special colors to be rendered with greater precision (relative to the real Pantone spot color) than is possible within the gamut available with only the process color inks.
Note that it is not possible to simulate all of the Pantone spot colors precisely with a CMYK or extended CMYKcm ink gamut.