Roblox Artist known as Contrastz showcased a cool project where he applies real acrylic paint to his Roblox models. Using a phone camera, the app captures the painting process and translates it directly onto the digital model, which can then be added into the game.
It would be interesting to learn how the whole process works, but in the meantime, you can check out more demos:
Contrastz previously used a variety of real-life materials to create Robox characters: