Examine source code of Play Elements

{
  "theme": {
    "images": {
      "theme_frame": "Firefox_Header_Elements_EmberHawk.jpg"
    },
    "colors": {
      "frame": "#fffd78",
      "tab_background_text": "#000000"
    }
  },
  "version": "2.0",
  "name": "Play Elements",
  "manifest_version": 2,
  "description": "A non-elegant, playful theme.\n\nDepicts the sun, sky, grass, and dirt."
}