Always love a good Turner livery.
I can't comprehend the panel check thing tho. What is it?
In the livery editor, the car is broken up into sections. Some cars vary, but most are...body, hood, wing, mirrors, and other. When you're on any of those sections, you can mash R3, and any part that's editable in the section you're on, will turn that aqua color. For that BMW, all the aqua parts are part of the body section.
Some cars have some interesting bits under the Other category, like chrome trim, and such. The roof of this BMW is under the Other section.