Examine source code of Color Picker Simple

{
  "manifest_version": 2,
  "name": "Color Picker Simple",
  "version": "1.0",
  "description": "Enter color code, save to personal palette, convert HEX/RGB",
  "permissions": [
    "storage"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "48": "color.png"
    }
  },
  "icons": {
    "48": "color.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{ebec309c-f8f5-43bb-bb7d-efebd7b62c66}"
    }
  }
}