title: What's so special in web sockets messages displayed with a green background in Chrome?
body: <p>Looking at web sockets at Stack Exchange, I notice that some messages are displayed with a green background in Chrome:</p>
  
  <p><img src="https://i.stack.imgur.com/GmMIt.png" alt="A screenshot of Network tab of Developer tools, showing messages with green background among ordinary messages with white background"></p>
  
  <p>What's so special in those messages? What are they?</p>