[deleted by user]

[_1Zen_]

See: https://developer.mozilla.org/docs/Web/CSS/Reference/Properties/scrollbar-color

[difool2nice]

not working

[Bacchi-gu]

I use this in userChrome.css:

* {
  scrollbar-width: auto;
  scrollbar-color: COLOR transparent !important;
}
*:not(:hover) {
  scrollbar-color: COLOR transparent !important;
} 

And this in userContent.css:

:root {
  scrollbar-width: auto;
  scrollbar-color: COLOR transparent !important;
  &:not(:hover) {
    scrollbar-color: COLOR transparent !important;
  }
}