I've recently acquired a Crusader tank for my garage:
![Crusader](https://i.stack.imgur.com/LiC2S.jpg)

It is very oppressive and white, and I would like to give it a paint job. However, like many authority vehicles it is apparently "not customizable". I'd leave it at that, if I were not previously able to customize a different kind of "not customizable" vehicle:
![Purple challenger](https://i.stack.imgur.com/AftSV.jpg)

I can assure you that the Challenger tank does not usually come in purple, but I can't for the life of me remember just how I managed to get it looking like that. Any advice would be most welcome.