chromium/chrome/test/data/banners/theme-color.html

<html>
  <head>
    <title>Manifest test app with theme color</title>
    <link rel="manifest" href="theme-color.json">
    <meta id="theme-color" name="theme-color" content="#ace">
    <script>
      window.onload = () => {
        navigator.serviceWorker.register('service_worker.js');
      };
    </script>
  </head>
  <body>
    Do-nothing page with a manifest and a service worker.
  </body>
</html>