I found out that, regardless of the mod you are using, it is impossible to change the type (color) of a license plate in your vehicle.
I tried several character vehicle swap mods but none of them seems to be able to actually remember the plate color and layout. After reloading the game, you are left with the same old, same old. Which is strange... Because all other upgrades and accessories are kept.
My guess is that one cannot modify the plates, due to the fact that Rockstar wants you to do it through the iFruit app and they somehow locked the possibility to do so during the game. Regardless of how counter-intuitive it may sound...
Editing the .ini files proved fruitless as well. Amusingly, I am able to change the plate numbers. Not the color however.
So back to the question - if you use any character vehicle modification... do you also have trouble getting your plate modified?
Can you imagine? I spent 150 bucks for a new license plate that fell off on my way back home!