Examine source code of Earth and Sky

{
  "theme": {
    "images": {
      "theme_frame": "FirefoxPersona_Sky-and-grass-and-buttercups_header.jpg"
    },
    "colors": {
      "frame": "#99ccff",
      "tab_background_text": "#0033ff"
    }
  },
  "version": "2.0",
  "name": "Earth and Sky",
  "manifest_version": 2,
  "description": "Sun and clouds and grass and buttercups."
}