I bought a decorative metal "planter" that hangs on the wall, like a half-bucket, I want to repaint it ? - whats special about bucket margarita mix

But we need to know to use to know what kind of color. It is painted beige with red markings, but I want to cover and change the color entirely. Is there a special paint or primer should I use and what should I do if I treat the water for the cultivation of a plant to live in it and want to test it?