Examine source code of Dark Lite marble

{
  "name": "Dark Lite marble",
  "manifest_version": 2,
  "version": "1.0",
  "theme": {
    "images": {
      "theme_frame": "firefox.bkg.marble.png"
    },
    "colors": {
      "frame": "rgba(255, 255, 255, 1)",
      "tab_background_text": "rgba(66, 66, 66, 1)",
      "toolbar_field": "rgba(87, 87, 87, 1)",
      "toolbar_field_text": "rgba(255, 255, 255, 1)",
      "tab_line": "rgba(0, 0, 0, 0)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{73f36e62-e187-4bef-9834-6fd0d249fa6e}"
    }
  }
}