Examine source code of Grayscale

{
  "theme": {
    "images": {
      "theme_frame": "Darkfox.png"
    },
    "colors": {
      "frame": "#383838",
      "tab_background_text": "#454545"
    }
  },
  "version": "2.0",
  "name": "Grayscale",
  "manifest_version": 2,
  "description": "The dark side of the firefox. A nice gradient touch too."
}