Open IV : Custom texture/livery won't work when it use a "ref" file

[Darnath 3]

I want to make, inter alia, a Sheriff version for this Impala but, when I load the car the ref texture is either confliting with the main or if I remove the ref and putt it on the main texture the livery appear all white where the ref file was intented.

(Some other models liveries loses textures at a certain distance)

 

Is there any tutorials or any tips on how to edit those kind of textures that use a ref instead of the "normal" way?

 

(The line "FLAG_HAS_LIVERY" is present, the vehicle is in the mod folder, there are no problems conserning textures loss, I've made a lot of custom liveries but when it has a ref I never found out how to do it)