With the roll cage installed, the player should have the option to paint the roll cage.
Yuwan Thayakaran on YouTube mentioned that it could keyword could already be a thing in Forza Horizon 6
Here’s the video I was mentioning earlier
That YouTuber’s vid sounds more like a what-if. Voted so devs can see this.
Well Yuwan Thayakaran mentioned that it could be an option and I myself said that it could be in the game but I did voted for it though nonetheless I just thought that everyone should know about it being a possibility so 
yeah 