Change popup background color

Hi, I’ve tried adding custom CSS to change the background color of the popup, so that it works together with the colors of my site https://www.magicwand.life.

I’ve tried adding the following code and variations thereof both to the custom CSS section in the plugin, and to the themes’ custom CSS section:

select#gtranslate_selector {background-color: #333366 !important;}

Nothing I’ve done so far to these sections changes anything. So what should I do?

An idea to improve the plugin and not get lots of questions about it (couldn’t find any previous here, as the search function returned nothing, hence I posted a new question, though when googling I’ve seen lots of people asking this question in variations) is to add a color selection section. Elements could be “Selector text”, “Selector Background”, and possibly corresponding elements for the menu item.

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