Examine source code of Firefox 2013 Logo Grey

{
  "theme": {
    "images": {
      "theme_frame": "header.png"
    },
    "colors": {
      "frame": "#d6dce1",
      "tab_background_text": "#000000"
    }
  },
  "version": "2.0",
  "name": "Firefox 2013 Logo Grey",
  "manifest_version": 2,
  "description": "A simple theme with the new Firefox logo with a blue-grey background. Email me at david.j.b@aol.com to request a background colour."
}