Examine source code of Colorize!

{
  "name": "Colorize!",
  "description": "Colorize tabs based on individual website theme-color!",
  "homepage_url": "https://github.com/JosephSamela/colorize-tabs",
  "version": "2.1resigned1",
  "icons": {
    "48": "icon48.png",
    "96": "icon96.png"
  },
  "manifest_version": 2,
  "permissions": [
    "theme",
    "tabs",
    "webNavigation"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{4c0cc3b6-b7fc-4017-879d-1941705423d7}"
    }
  }
}