Examine source code of Gnome Professional

{
  "name": "Gnome Professional",
  "manifest_version": 2,
  "version": "1.0",
  "theme": {
    "images": {
      "theme_frame": "empty-pixel.png"
    },
    "colors": {
      "frame": "rgba(96, 96, 96, 1)",
      "tab_background_text": "rgba(224, 224, 224, 1)",
      "toolbar": "rgba(67, 67, 67, 1)",
      "bookmark_text": "rgba(224, 224, 224, 1)",
      "toolbar_field": "rgba(97, 97, 97, 1)",
      "toolbar_field_text": "rgba(224, 224, 224, 1)",
      "tab_line": "rgba(52, 120, 203, 1)"
    }
  }
}