Examine source code of Rainbow thing

{
  "theme": {
    "images": {
      "theme_frame": "rainbowthing.png"
    },
    "colors": {
      "frame": "#000000",
      "tab_background_text": "#ffffff"
    }
  },
  "version": "2.0",
  "name": "Rainbow thing",
  "manifest_version": 2,
  "description": "Random persona made with <a href=\"https://outgoing.prod.mozaws.net/v1/27597fb86425e97bab24d0abab3630ebe35de78c319b3a868f23a9ca59f2fd3a/http%3A//Paint.NET\" rel=\"nofollow\">Paint.NET</a>"
}