Examine source code of Newspaper grey

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Newspaper grey",
  "theme": {
    "images": {},
    "properties": {},
    "colors": {
      "toolbar": "rgb(204, 204, 204)",
      "toolbar_text": "rgb(60, 60, 60)",
      "frame": "rgb(60, 60, 60)",
      "tab_background_text": "rgb(255, 255, 255)",
      "toolbar_field": "rgb(255, 255, 255)",
      "toolbar_field_text": "rgb(60, 60, 60)",
      "tab_line": "rgb(204, 204, 204)",
      "popup": "rgb(255, 255, 255)",
      "popup_text": "rgb(60, 60, 60)",
      "tab_loading": "rgb(204, 204, 204)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{980e8e96-2a00-4220-9cd6-7b773743dd5d}"
    }
  }
}