(FIRST)
I tried it myself in painting the whole graphic in one colour and changing it bit by bit - so to find out what area belogs to what model-area.
The sel or cel is a picture with several layers in Paintshop Pro. Here's the only one I could find (for the amazon)
http://www.game-over-media.de/pc/darkstone/Amazone.zip - you'll need PSP to see the layers and descriptions.
(SECOND)
Making monster skins isn't as easy as making character skins. And there aren't any manuals about it i know. There was a project at
http://skinztones.free.fr/ but i think it's been frozen.