I added their own slots and named them: "lspdk91" for the charger and "lspdk92" for the tahoe. In the end, I ended up just dropping the mods and removing them from the game because I couldn't figure it out.
Though, after some further modding I came across the same exact problem again (though without the weird color on the rims) with the tahoe from the "Special Weapons And Tactics [SWAT] Pack". This time, I decided to do a bit more digging around and I was able to fix the issue by pretty much creating an entire dlc pack for these vehicles like other vehicles packs do. I pretty much just copied the files from another dlc pack, filled in the new vehicle model name (in meta files and content.xml/setup.xml files), and then copied over the metas for the vehicles that the SWAT Pack provides. When I tested the tahoe in-game after doing all of this the vehicle no longer had any green color.
If you want me to go into more details on how I created the dlc pack for you to try yourself, ask and I'll help you out to the best of my knowledge.