The simulator has the technology to be able to simply select/change the specific colors for an aircraft livery. These files are the “…AIRFRAME_LIVERYCOLOR…” or “…AIRFRAME_DECALS…” files. I’ve tested this by editing various aircraft colors solely by recoloring these files.
A simple UI should allow the selection of paint color from a digital color pallet that replaces the associated color in the respective file, and save, compile, and refresh these user selected textures.