Examine source code of Background color

{
  "manifest_version": 2,
  "name": "Background color",
  "version": "1.0",
  "description": "A shortcut to change background color in Firefox. It has light on dark, dark on pink and original. The shortcut is ctrl + shift + u.",
  "icons": {
    "48": "icons/bgcolor-48.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "background_color.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "backgroundcolor@mathiashh.dk"
    }
  }
}