set a Focusring around a popupmenu invisible or off

how can i get rid of the focus ring or how can i turn the blue lines around the pup up menu off or invisible

CSS

https://www.tjvantoll.com/2013/01/28/stop-messing-with-the-browsers-default-focus-outline/

i did it around the textfield but how can i set it at the popup menu?