Examine source code of Deep underneath

{
  "theme": {
    "images": {
      "theme_frame": "upperbannerfirefox.jpg"
    },
    "colors": {
      "frame": "#db2828",
      "tab_background_text": "#ed0c0c"
    }
  },
  "version": "2.0",
  "name": "Deep underneath",
  "manifest_version": 2,
  "description": "Firefox embraces the inside of the earth"
}