It must be a special color, it must be heat-resistant, so that your whole house does not stink when you flood. It is necessary to degrease them with something, then they can be painted right away. I have them in the basement made of copper, but after the apartment I have them painted white to match the radiators. The paint cost about 300 CZK one small can: - ((I have them stuck in the wall, they stick to them just a short distance from the radiator and one can was enough for the whole house, I painted it twice.