Thunderbird_91_ESR/config/config.css
/* Thunderbird userChrome.css tweaks ************************************************************/
/* Github: https://github.com/aris-t2/customcssfortb ********************************************/

:root {
  /* tab_height.css */
  --tab-min-height: 26px !important;
  
  /* tab_border_radius.css */
  --tabborderradius: 3px !important;
  
  /* window_header_colors.css */
  --header_background_color: #202340 !important;
  --header_text_color: #ffffff !important;
  --header_caption_button_color: rgba(255,255,255,0.3) !important;
  
  /* mail_panel_color.css */
  --mailpanel_background_color: #ffffff !important;
  --mailpanel_text_color: #000000 !important;

  /* classic_appbutton.css */
  --appbuttonlabel: "Thunderbird" !important;
  --appbuttoncolor1: #33CCFF !important;
  --appbuttoncolor2: #3366FF !important;
  --appbuttontextcolor: #FFFFFF !important;
  --appbuttontextshadowcolor: #000000 !important;
  
  /* ctb_button_size_main_toolbars.css */
  --ctb_maintoolbar_button_height: 0px !important;
  --ctb_maintoolbar_button_width: 0px !important;
  
  /* ctb_button_size_menubar.css */
  --ctb_menubar_button_height: 0px !important;
  --ctb_menubar_button_width: 0px !important;
}