What combination of paint colors give you a pot that looks like old?

Old? Patina ? I would go with green , brown and a dark orange.

www.hometalk.com/diy/paint/easy-galvanized-metal-aging-technique-10279422

I made a Goodwill pot look like one of those aged italian pots from Pier One by using chalk paint in a brown color I liked that looked like clay. I painted the pot in a dark brown using just acrylics I had on hand. After the paint dried, I wiped vaseline on the pot in areas where I wanted it to look like the paint had chipped or become worn. Then painted with my lighter clay colored chalk paint over the whole pot and used a cloth to wipe away the vaseline. What happens is the vaseline wipes away with the chalk paint and the darker brown color underneath comes through these spots and it looks chipped and aged.