Paint isn’t free no matter what kind, no. As was mentioned, standard paints are free, for most manufacturers metallic paints are too – but not all of them. Usually you don’t get charged full amount though, i recall someone paying £100 or something like that towards a metallic paintjob. “Special”, or premium paints are usually out of pocket, like Oryx white etc.
But, absolutely you should be told the price before you sign the contract. They usually sit down with you, go through the list and tell you the price. The GTD currently is £2850 AP.