HP PCL/PJL reference (PCL 5 Color) - Technical Reference Manual

EN Using Palettes (Color LaserJet, 5, 5M, DeskJet) C-5
Palette Management by ID
All palettes have a unique ID (identification number). The default
black and white palette created on power-up or
?E has an ID of 0.
Palette management by ID lets applications have multiple palettes. As
shown below, multiple palettes can exist in two areas: the palette
stack and the palette store. The stack holds palettes that are pushed
via a Push/Pop Palette command; the store holds palettes having
palette IDs.
Palettes on the stack may not be selected by ID, since only a copy of
a palette is pushed onto the stack; the original palette and ID remain
in the palette store. A palette popped from the stack goes into the
palette store, becomes the new active palette, and assumes the ID of
the previously active palette, which is overwritten. Only one palette at
a time may be active.