how did you get the color to change? Own AO + mtl + mdl? just doing 6x mdl is not enough.
Which mod can I look at?
Yup, own mtl and mdl is my method, and to a certain degree yes also own AO.
I do however design the models in a way that the meshes are (mostly) per material, hence I can use generic materials for the car paint across my models. So for each colour then have an mdl file that has a distinct material for the car body, but all others are (usually) the same.
I expect you have one mesh everything but the body. It might be easier when you make a separate mesh for the body.
oh PS; e.g. see my cars of the 90's or 00's or VW T3 pack, although there the random selection in the .con is quite different, the model part is the same. I just don't usually use sequence numbers on the mdl naming, Think in the VW base pack I did.