Examine source code of Red Barn...

{
  "name": "Red Barn...",
  "manifest_version": 2,
  "version": "4.0",
  "theme": {
    "images": {
      "theme_frame": "RedBarnH.jpg"
    },
    "colors": {
      "frame": "rgba(173, 152, 160, 0.88)",
      "tab_background_text": "rgba(0, 0, 0, 1)",
      "toolbar": "rgba(173, 152, 159, 0)",
      "bookmark_text": "rgba(255, 255, 255, 1)",
      "toolbar_field": "rgba(214, 207, 160, 0.07)",
      "toolbar_field_text": "rgba(255, 255, 255, 1)",
      "tab_line": "rgba(0, 0, 0, 1)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{71b29c08-1725-4598-981c-65711ba5169f}"
    }
  }
}