Prominent tab color for Firefox container

README.md

1. Go to about:config, enable these flags:
   • toolkit.legacyUserProfileCustomizations.stylesheets
   • layout.css.color-mix.enabled
2. Go to about:support, look for profile folder.
3. Add the CSS below to chrome/userChrome.css inside the profile folder.

userChrome.css

/**/
.tabbrowser-tab[usercontextid] .tab-context-line {
  display: none;
}
.tabbrowser-tab[usercontextid] .tab-background {
  background: var(--identity-tab-bgcolor) !important;
  border: 1px solid var(--identity-tab-border-color);
  box-shadow: 0 0 4px var(--identity-tab-shadow-color) !important;
}
.tabbrowser-tab[usercontextid] {
  --identity-tab-bgcolor: color-mix(in srgb, var(--identity-tab-color) 20%, transparent);
  --identity-tab-border-color: color-mix(in srgb, var(--identity-tab-color) 50%, transparent);
}
.tabbrowser-tab[usercontextid]:hover {
  --identity-tab-bgcolor: color-mix(in srgb, var(--identity-tab-color) 30%, transparent);
}
.tabbrowser-tab[usercontextid][selected] {
  --identity-tab-bgcolor: color-mix(in srgb, var(--identity-tab-color) 50%, var(--tab-selected-bgcolor, var(--toolbar-bgcolor)));
  --identity-tab-border-color: color-mix(in srgb, var(--identity-tab-color) 90%, currentColor);
  --identity-tab-shadow-color: var(--identity-tab-color, #000);
}
/**/