The "V1.3" update typically focuses on compatibility with the latest game versions and expanding the variety of supported vehicles.
Note that many ETS2 skin packs are incompatible with American Truck Simulator (ATS) unless specifically stated, due to different truck models. COCA-COLA SKINPACK OD MR.FOX V1.3
For trailers, go to your , select an owned trailer, and use the "Paint Job" menu in the customization screen. The "V1