Change Icon when Menu is opened

Hi – i use the PRO-Option “Burger Button Image” on this Site, developing for a Customer. The Side is mainly b/w only, so the Background-Color is set to white. The Burger Button Image is also white, cause the Menu Burger lies over a b/w-Movie. If you activate the Menu, you can’t see the Burger Menu, cause its white on white. Is there any possibility to change the Burger Button Image in “opened” state? Another Solution?

The page I need help with: [log in to see the link]