driver.get('http://www.httpbin.org')
time.sleep(2)
driver.execute_script(
    'document.getElementsByClassName("mp")[0].style.background = "green"')
driver.save_screenshot('testing1.png')
driver.get('http://www.kahoot.it')
time.sleep(2)
driver.execute_script(
    "var body = document.getElementsByTagName('body')[0]; body.setAttribute('background-color', 'white')"
    )
driver.execute_script('document.body.style.background = "black"')
driver.save_screenshot('testing2.png')
Прозрачный скриншот с PhantomJS в Selenium [Python]?