Examine source code of Autumn presents

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Autumn gifts",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.jpg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "center center"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgba(223, 235, 213, 0.5)",
      "toolbar_text": "rgb(160, 54, 0)",
      "frame": "rgb(255, 252, 240)",
      "tab_background_text": "rgb(0, 0, 0)",
      "toolbar_field": "rgb(255, 252, 240)",
      "toolbar_field_text": "rgb(0, 103, 125)",
      "tab_line": "rgb(143, 213, 22)",
      "popup": "rgba(239, 237, 217, 0.8)",
      "popup_text": "rgb(83, 38, 0)",
      "ntp_background": "rgba(223, 235, 213, 0.5)",
      "tab_loading": "rgb(143, 213, 22)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{127393dd-abad-4e0e-a0a1-691cef178077}"
    }
  }
}