To be honest i'm only sort of following what you are saying. But I believe wow does not use a colour palette. These .blp textures are converted .png files, you can easy convert one of these blp's with blpconverter's found on this website or install blpview to see these files in your windows explorer.
For particle's , some of the particles do use rgb codes to create particle colors.
For example this cape uses this texture: https://www.wowhead.com/item=152154/gilded-seraphs-drape?bonus=3612:1475
And to create one of these texture files, is pretty "simple". If you know how to draw these you can make one yourself, although I am not much of a designer. But there are easy ways to recolor the blizzard blp and make items have an entirely different look.
As for example the warglaives ?