I had this up for a year and there was very little color change, even being next to salt water! So, in an attempt to mask what was clearly obvious to the renters next door(bad situation) that I wanted it to go green. I tried several methods to get the copper to turn a nice verdigris but when I combined 2 of them it was instant. Vinegar, by itself did very little, saltwater from the bay did very little, BUT COMBINED it was instant
I took a pressure washer to it last summer since the house next door went from rental to new owner/occupied (nice folks). It barely phased the several years of green.
It looks like Wrights and a large random orbit buffer, like for my car, might work! Next summer it will happen, if not sooner because it might be good shoulder rehab exercise