Painting inside of bonsai pots

[vincepena23]

Been stusying Bonsai for 4 months now. I have 8 indoor trees and plan on creating bonsai pots of my own, using cement. I see videos on youtube of people making them with molds and wiring. At the end they paint them of course. The inside of the pot as well. I keep wondering what kind of paint they are using. It has to be nontoxic, being the paint won't leech into the soil, once a tree has been planted and watered over and over.

Any advice as to what kind of paint to use? Water based, acrylic?