How to change background colour of utility menu?

[Beleth-D]

Hello everyone,
how to change background colour of utility menu?
Thanks ❤️

[black7375]

Are you modifying userChrome.css and not the theme?
Consider utilizing the following code

#main-window {
  --arrowpanel-background: red !important;
  --arrowpanel-color: blue !important;
  --arrowpanel-border-color: yellow !important;
}

[Beleth-D]

Yes, it works perfectly!
Thanksss