Examine source code of Happy, blue sky

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Happy sky",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/bg-012-1e971c5fbb8dec3acbd76dd6c6819de9.svg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(255, 255, 255)",
      "toolbar_text": "rgb(0, 0, 0)",
      "frame": "rgb(173, 215, 255)",
      "tab_background_text": "rgb(0, 0, 0)",
      "toolbar_field": "rgb(246, 246, 246)",
      "toolbar_field_text": "rgb(91, 91, 91)",
      "tab_line": "rgb(255, 223, 87)",
      "popup": "rgb(255, 223, 87)",
      "popup_text": "rgb(0, 0, 0)",
      "popup_highlight_text": "rgb(0, 0, 0)",
      "popup_highlight": "rgb(223, 223, 223)",
      "toolbar_field_highlight": "rgb(255, 223, 87)",
      "tab_loading": "rgb(255, 223, 87)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{12b7d84b-0c8e-43bb-8799-06deb5ab36b9}"
    }
  }
}