Examine source code of Google Dark Mode

{
  "name": "Google Dark Mode",
  "manifest_version": 2,
  "version": "1.0",
  "theme": {
    "images": {
      "theme_frame": "firefox theme black square.png"
    },
    "colors": {
      "frame": "rgba(43, 43, 43, 1)",
      "tab_background_text": "rgba(199, 199, 199, 1)",
      "toolbar": "rgba(60, 60, 60, 1)",
      "bookmark_text": "rgba(199, 199, 199, 1)",
      "toolbar_field": "rgba(40, 40, 40, 1)",
      "toolbar_field_text": "rgba(199, 199, 199, 1)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{6aee42d9-d10a-420b-a727-9d953f029cc2}"
    }
  }
}