HP Color LaserJet 4600 Printer series - Manual (Page 131)

ENWW 117
Some swatch books are created from spot colors. Spot colors are
specially created colorants. Many of these spot colors are outside of
the gamut of the printer. Most spot color swatch books have
companion process swatch books that provide CMYK approximations
to the spot color.
Most process swatch books will have a note on what process
standards were used to print the swatch book. In most cases they will
be SWOP, EURO, or DIC. To get optimal color matching to the
process swatch book, select the corresponding ink emulation from the
printer menu. If you cannot identify the process standard, use SWOP
ink emulation.