People always chase the button colour, but the bigger thing is not using your CTA colour anywhere else. If green is your action colour then dont use green for badges, icons, trust ticks, headings etc... otherwise you train the eye to ignore it. Base can be boring as hell, just make the action colour rare and obvious. Also worth matching the general mood of the ad/angle a bit, cause a lander that looks totally different from the click source can feel sketchy even if the colours are “high converting”.