Examine source code of Grey on Grey

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Grey on Grey",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/bg-000-5672c42860d5b06e1058dc477397f3ef.svg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(78, 77, 77)",
      "toolbar_text": "rgb(235, 238, 236)",
      "frame": "rgb(59, 60, 59)",
      "tab_background_text": "rgb(162, 164, 162)",
      "toolbar_field": "rgb(56, 57, 56)",
      "toolbar_field_text": "rgb(235, 238, 236)",
      "tab_line": "rgb(75, 77, 75)",
      "popup": "rgb(78, 77, 77)",
      "popup_text": "rgb(235, 238, 236)",
      "tab_selected": "rgb(120, 120, 120)",
      "tab_text": "rgb(235, 241, 235)",
      "toolbar_bottom_separator": "rgb(84, 86, 86)",
      "toolbar_top_separator": "rgb(78, 77, 77)",
      "tab_loading": "rgb(75, 77, 75)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{69e1f2d4-a8a6-4772-bb92-cf0bf479a2ef}"
    }
  }
}