Examine source code of Blue september

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Blue september",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/bg-005-f5f3cf677b1f132c75ddc7bd319dd1fc.svg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(206, 233, 248)",
      "toolbar_text": "rgb(2, 81, 140)",
      "frame": "rgb(14, 131, 228)",
      "tab_background_text": "rgb(9, 28, 87)",
      "toolbar_field": "rgb(255, 255, 255)",
      "toolbar_field_text": "rgb(2, 128, 167)",
      "tab_line": "rgb(6, 55, 154)",
      "popup": "rgb(143, 203, 248)",
      "popup_text": "rgb(15, 101, 136)",
      "tab_loading": "rgb(6, 55, 154)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{6ac21f6a-74e7-417f-8164-21bf783a9192}"
    }
  }
}