Examine source code of ColorfulTabs

{
  "manifest_version": 2,
  "name": "ColorfulTabs",
  "short_name": "ColorfulTabs",
  "description": "Let's try to re-color the tabs. Shall we? Currently only colors the selected tab due to https://bugzilla.mozilla.org/show_bug.cgi?id=1320585",
  "version": "34.8",
  "icons": {
    "16": "icon-16.png",
    "48": "icon-48.png",
    "128": "icon-128.png"
  },
  "author": "Shivanand Sharma",
  "homepage_url": "https://www.addongenie.com/",
  "background": {
    "page": "background.html"
  },
  "options_ui": {
    "page": "options.html"
  },
  "browser_action": {
    "default_icon": "icon-48.png",
    "default_popup": "popup.html"
  },
  "sidebar_action": {
    "default_title": "",
    "default_icon": {
      "16": "icon-128.png",
      "20": "icon-128.png",
      "24": "icon-128.png"
    },
    "default_panel": "sidebar.html",
    "browser_style": true
  },
  "content_security_policy": "script-src 'self'; object-src 'self'",
  "applications": {
    "gecko": {
      "strict_min_version": "57.0",
      "id": "{0545b830-f0aa-4d7e-8820-50a4629a56fe}"
    }
  },
  "permissions": [
    "contextMenus",
    "menus",
    "tabs",
    "theme",
    "storage",
    "<all_urls>"
  ]
}