To achieve a patina aesthetic, I recommend using tones in the turqouise and teal family, along with your moodier, darker colors. When you envision old, rusted, and oxidized metals, the colors can vary but it is common to see tones of greens and even blues.
I’m using Reflecting Pool by Sherwin Williams (a vibrant aqua color) to make my patina statement on this piece. Again I will apply the paint by dabbing the brush up and down to create lots of texture.