Examine source code of Steam Modern

{
  "manifest_version": 2,
  "version": "1.1",
  "name": "Steam Modern",
  "theme": {
    "images": {},
    "properties": {},
    "colors": {
      "toolbar": "rgb(27, 40, 56)",
      "toolbar_text": "rgb(199, 213, 224)",
      "frame": "rgb(23, 26, 33)",
      "tab_background_text": "rgb(102, 192, 244)",
      "toolbar_field": "rgb(42, 71, 94)",
      "toolbar_field_text": "rgb(199, 213, 224)",
      "tab_line": "rgb(102, 192, 244)",
      "popup": "rgb(42, 71, 94)",
      "popup_text": "rgb(199, 213, 224)",
      "tab_loading": "rgb(102, 192, 244)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{99d823ff-fe3f-432a-809f-2ae0c9431d11}"
    }
  }
}