UltraSkeuo/source/common/desktop_environment_fixes.scss

// XFCE system tray buttons don't look good without margin
.xfce4-panel #sn-button {
  margin: 1px;
}

#docklike-plugin {
    button {
        background-color: transparent;
        .active_group & {
            @extend %button-pressed;
            background-color: red;
        }
    }
    
}