Don't have access to the game/UI to check right now, but references to them might be in ImageStyles.xml. They might be at least partly referenced in proxyactor.xml since they're used by the overhead display, and probably the target/implied target window.
Easiest way to backtrace is to fire up UIBuilder, go to the target or implied target window and find the elements there and see what image or imagestyle is called.
Color wise I imagine they are recolored automatically in game, so only 1 base image for each and then the game handles the tinting, like it does with item icon backgrounds.
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