FUEL: REFUELED is an enhancement modification for the game FUEL, which brings multiple bug-fixes, improvements and the addition of various new content.
This was only quickly made to highlight the point about how V15.3 has a more open file structure that allows swapping out individual scripts (such the color palette for a specific vehicle) via the mod manager.
Everyone has their own favorite colors - V15.3 will allow you to change the ten RGB colors available for a single (or all) vehicle outside the game and even swap between schemes via the mod manager. If you have a good color scheme then upload it to the forums and it may become included as an installation option in a future release of FUEL: REFUELED (or people can just download them individually and install as they wish).
The whole point of this exercise wasn't to allow just vehicle colors to be changed, but rather installing content such as custom tracks.