Examine source code of DarkMap

{
  "name": "DarkMap",
  "manifest_version": 2,
  "version": "1.0",
  "theme": {
    "images": {
      "theme_frame": "2910865.jpg"
    },
    "colors": {
      "frame": "rgba(79, 79, 79, 1)",
      "tab_background_text": "rgba(255, 255, 255, 1)",
      "toolbar": "rgba(56, 56, 56, 1)",
      "bookmark_text": "rgba(199, 199, 199, 1)",
      "toolbar_field": "rgba(0, 0, 0, 1)",
      "toolbar_field_text": "rgba(166, 166, 166, 1)",
      "tab_line": "rgba(77, 77, 77, 1)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{6854ce77-44ee-498d-b7f0-63b88d2471ee}"
    }
  }
}