When applying decals I don’t seem to be able to match the car colour. For example, paint your car, note the values, then try apply any shape with that exact colour. The colour just doesn’t match. I’ve got quite a few logos/designs that depend on being able to do this. Seem to remember previous games this worked fine.
Best way to remedy this is to put a base layer down that covers entire car… Place layer groups on that base vinyl rather that directly on the paint. Hope this helps you.