Examine source code of RoosterColor

{
  "manifest_version": 2,
  "name": "Roostercolor",
  "version": "1.1.0",
  "description": "A browser extension that enables custom colors for courses on rooster.rug.nl",
  "browser_specific_settings": {
    "gecko": {
      "id": "roostercolor@tijnedens.com",
      "strict_min_version": "55.0"
    }
  },
  "icons": {
    "16": "icons/icon_16.png",
    "32": "icons/icon_32.png",
    "48": "icons/icon_48.png",
    "128": "icons/icon_128.png"
  },
  "background": {
    "scripts": [
      "src/background.js"
    ],
    "persistent": false
  },
  "browser_action": {
    "default_title": "Roostercolor",
    "default_icon": "icons/icon_48.png"
  },
  "permissions": [
    "storage",
    "activeTab",
    "tabs"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://rooster.rug.nl/*"
      ],
      "js": [
        "lib/tinycolor.js",
        "src/contentScript.js"
      ],
      "css": [
        "src/injectedStylesheetRC.css"
      ]
    }
  ]
}