Materials

Each vehicle is made up of multiple parts. Each body part uses more than one material, allowing you to have different colours around the body.

Here's an example from the front of Car_01.

You could select the 'Car_01_Dark' material and edit the colour on that, however, do be aware that this material is used on more than one GameObject so will change the colour everywhere this is used.

I suggest creating a new material and assigning that into any material slots you want to use that colour.