Paint the car. (Final Fantasy 15)

I want to paint the car black, but it requires black/blue/green ore. Of course it is logical that the ore extracted from the mines on the map, but the third Chapter has come from the mines and drop out only fragments of stones of all colors, and in the shop it require ore and I don't quite understand where can I get ore? Can these pieces as you can into the ore to turn? or where do get it colored ore?