I could be wrong but a championship designates a car though it's slot and doesn't allow you to change it during a season. So i wouldn't be surprised if you have the same car throughout the championship. If the livery changes are in the same slot i think you are able to use different versions of a car in championship
I don't know how the different versions are setup but if it uses multiple slots it's probably a no go.
stuck in same graphics thru a World Championship season