Examine source code of Mostly flat

{
  "manifest_version": 2,
  "version": "1.2",
  "name": "Mostly flat",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/bg-000-5672c42860d5b06e1058dc477397f3ef.svg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(40, 44, 52)",
      "toolbar_text": "rgb(234, 234, 234)",
      "frame": "rgb(40, 44, 52)",
      "tab_background_text": "rgb(234, 234, 234)",
      "toolbar_field": "rgb(31, 33, 35)",
      "toolbar_field_text": "rgb(221, 226, 237)",
      "tab_line": "rgb(234, 234, 234)",
      "popup": "rgb(32, 32, 32)",
      "popup_text": "rgb(234, 234, 234)",
      "icons_attention": "rgb(234, 234, 234)",
      "sidebar_border": "rgba(32, 32, 32, 0)",
      "sidebar": "rgb(40, 44, 52)",
      "toolbar_bottom_separator": "rgba(32, 32, 32, 0)",
      "toolbar_field_border_focus": "rgba(234, 234, 234, 0.85)",
      "toolbar_top_separator": "rgba(32, 32, 32, 0)",
      "toolbar_vertical_separator": "rgb(234, 234, 234)",
      "tab_loading": "rgb(234, 234, 234)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{52883fc0-4b95-41d4-9e1f-7bd106308f6a}"
    }
  }
}