The custom palettes are resource files in GFF format, of type ITP.
It may be helpful while reading this document to have
Torlack's nwnexplorer program
open on a module file with a few entries in a custom
palette. Look under the category 'Blueprint Palettes'.
You should also be familiar with
Torlack's description of the GFF format
(though he calls it ITP)
The root entry has one child element called MAIN, of LIST type.
The file represents a tree. There are three types of nodes in the tree: terminals, non-terminals, and entity descriptors. Non-terminals may not contain entity definitions, they may only contain a list of other non-terminal nodes. Terminals may only contain entity definitions, not other non-terminals nor terminals.
Non-terminal nodes contain two elements.
STRREF but of type UINT32, somehow
indicating the name of the category the node represents. It is an
index into the dialog.tlk string table.
LIST, of type LIST>, containing the child entry nodes.
A terminal node has the same two child elements as a non-terminal
node, with the addition of a UINT8 named ID. All
terminal nodes have a unique ID. The entity blueprint resources refer
back to their palette node with a property PaletteID also
of type UINT8, containing that number.
However, for a terminal node, the LIST element contains only entity
descriptors. The contents of an entity descriptor depend upon the
type of palette. For all palettes, there is a STRING named
NAME, and a RESREF named RESREF. Creatures
have two more, CR and FACTION, but they are
not relevant to us.