The AB test example where everything was kept the same except the color of the button should be taken with a grain of salt. Many elements on the page are green

The AB test example where everything was kept the same except the color of the button should be taken with a grain of salt. Many elements on the page are green and there's almost no trace of red, so obviously changing the button color to red would instantly make it stand out more. That's an issue of contrast, not color preference.