SweetTokyoNight/gtk-3.0/apps/_mate.scss

.mate-panel-menu-bar,
panel-toplevel.background {

  &, menubar { background-color: opacify($panel_bg_color, 1); }

  menubar,
  #PanelApplet label,
  #PanelApplet image { color: $panel_fg_color; }

  // Panel buttons
  button:not(#tasklist-button) {
    @extend %panelbutton;
  }

  button,
  #tasklist-button {
    label, image { color: inherit; }
  }

  .wnck-pager {
    color: mix($panel_fg_color, black, 50%);
    background-color: darken($panel_bg_color, 3%);

    &:hover {
      background-color: lighten($panel_bg_color, 5%);
    }

    &:selected {
      color: lighten($selected_bg_color, 20%);
      background-color: $selected_bg_color;
    }
  }

  na-tray-applet {
    -NaTrayApplet-icon-padding: 0;
    -NaTrayApplet-icon-size: 16px;
  }
}

//
// Mate OSD Window
//

MsdOsdWindow.background.osd {
    border-radius: 2px;
    border: 1px solid $borders_color;
  
    .progressbar {
      background-color: $selected_bg_color;
      border: none;
      border-color: $selected_bg_color;
      border-radius: 5px;
    }
    .trough {
      background-color: darken($osd_bg_color, 5%);
      border: none;
      border-radius: 5px;
    }
  }