Re: Using css to change header logo image
Each color style has its own bg.gif image inside the color folder. If you want the red header to have a car, change the red/images/bg.gif to have a car, and then edit or leave the blue/images/bg.gif AND the /images/bg.gif to be another image. Since blue is the default for the Blue theme, you need to change it both places, unless you want it different depending on your wishes.
WordPress customizer - graphic design
Petersen Media Group