Examine source code of Marbled

{
  "theme": {
    "images": {
      "theme_frame": "Marbles-top.jpg"
    },
    "colors": {
      "frame": "#2b2b2b",
      "tab_background_text": "#ffffff"
    }
  },
  "version": "2.0",
  "name": "Marbled",
  "manifest_version": 2,
  "description": "Created with POV-Ray and then edited with <a href=\"https://outgoing.prod.mozaws.net/v1/27597fb86425e97bab24d0abab3630ebe35de78c319b3a868f23a9ca59f2fd3a/http%3A//Paint.NET\" rel=\"nofollow\">Paint.NET</a>."
}