Examine source code of KidZania Background

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "KidZania Background",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.png"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "right top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(244, 139, 0)",
      "toolbar_text": "rgb(172, 0, 51)",
      "frame": "rgb(244, 139, 0)",
      "tab_background_text": "rgb(172, 0, 51)",
      "toolbar_field": "rgb(172, 0, 51)",
      "toolbar_field_text": "rgb(244, 139, 0)",
      "tab_line": "rgb(172, 0, 51)",
      "popup": "rgba(244, 139, 0, 0.53)",
      "popup_text": "rgb(121, 0, 39)",
      "tab_loading": "rgb(172, 0, 51)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{56b5b3b7-6c81-4680-a78f-2343bc50f5ef}"
    }
  }
}