It's a rubber compound. You can buy stickers that go over the existing switch gear like this:
https://www.ebay.co.uk/itm/394651879019?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=avueyyaerko&sssrc=4429486&ssuid=IE07kO4STZy&var=&widget_ver=artemis&media=COPY