samples/javascript_es6/70.styling-webchat/index.html

<!DOCTYPE html>
<html lang="en-US">
  <head>
    <title>Web Chat: Customizing thru style options</title>
    <script type="text/javascript" src="https://cdn.botframework.com/botframework-webchat/master/webchat.js"></script>
    <style>
      html, body { height: 100% }
      body { margin: 0 }

      #webchat,
      #webchat > * {
        height: 100%;
        width: 100%;
      }
    </style>
  </head>
  <body>
    <div id="webchat"></div>
    <script>
      const styleOptions = {
        backgroundColor: 'Black',
        bubbleBackground: '#222',
        bubbleBorder: 'solid 1px #444',
        bubbleBorderRadius: 20,
        bubbleFromUserBackground: '#222',
        bubbleFromUserBorder: 'solid 1px #444',
        bubbleFromUserBorderRadius: 20,
        bubbleFromUserTextColor: 'White',
        bubbleTextColor: 'White'
      };

      window.WebChat.renderWebChat({
        directLine: window.WebChat.createDirectLine({ secret: 'YOUR_BOT_SECRET_FROM_AZURE' }),
        styleOptions
      }, document.getElementById('webchat'));
    </script>
  </body>
</html>