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

3-10 Using Palettes EN
The Palette Control command provides a way of managing system
memory by deleting palettes in either the stack or store that are no
longer in use.
Palette Control that is exercised during macros can have significant
impact on palettes that exist within the system. Deleting all palettes,
or those on the stack, or the current palette, or all those except on the
stack can have adverse effects when the macro is exited. The
adverse effect could be the deletion of the desired palette, and
replacement with a black and white non-programmable palette.