Examine source code of ColorMemory

{
  "manifest_version": 2,
  "name": "ColorMemory",
  "version": "1.0",
  "description": "Capture dominant colors when hovering images and save palettes to a Color Board. Copy HEX easily.",
  "icons": {},
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "color-memory.js"
      ],
      "css": [
        "color-memory.css"
      ],
      "run_at": "document_end"
    }
  ],
  "permissions": [
    "storage",
    "activeTab"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{5e4c4604-5b2a-4430-98b2-9f709a760db7}"
    }
  }
}