Examine source code of Nile Blue

{
  "name": "Nile Blue",
  "description": "Nile Blue Theme For Firefox + You can changed colors",
  "homepage_url": "https://github.com/rty65tt/firefox-theme-nileblue",
  "manifest_version": 2,
  "version": "1.9",
  "short_name": "nilebluetheme",
  "icons": {
    "48": "icon.png"
  },
  "permissions": [
    "theme",
    "storage"
  ],
  "background": {
    "scripts": [
      "setsettingstheme.js"
    ]
  },
  "options_ui": {
    "page": "options/index.html"
  },
  "applications": {
    "gecko": {
      "id": "nilebluetheme@rty65tt.org",
      "strict_min_version": "60.0"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "*://*/*"
      ],
      "css": [
        "scroll.css"
      ],
      "match_about_blank": true,
      "all_frames": true
    }
  ]
}