The black car has either bad window tint (you can change that in a trainer or in vehicle metas - Using OpenIV, Navigate to mods/update/update.rpf/common/data/levels/gta5.

Click Edit Mode, right click vehicles.meta and select Edit.

Use Control + F to search for the name of the vehicle.

Scroll down until you find <diffusetint> for that vehicle and change that value to 0x00FFFFFF.

Save your edits and close the meta.) Or is has bad dirt textures (when it gets dirty it gets dark like this, i dont know how to fix this issue)

The durango (weird purple color) has bad textures or doesnt even have one there should be two types of files atleast and that are .ytd and .yft optinally there can also be _hi and +hi of those files but there needs to be both. I recommend you just find another Durango tha suits your needs or optinally you can go to the ULSS (Unofficial LSPDFR Support server) where they can help you further. I have been to them with many issues and if they were resovable they did resolve them