style.css

@namespace url(http://www.w3.org/1999/xhtml);

@-moz-document url("https://scratch.mit.edu/messages/"), url("https://scratch.mit.edu/messages") {
  .social-message {
    border-bottom-color: #C5C5C5;
  }
  
  .social-message.mod-forum-activity {
    background-color: hsl(300, 55%, 92%);
  }
  
  .social-message.mod-comment-message,
  .social-message.mod-follow-user {
    background-color: hsl(215, 100%, 90%);
  }
  
  .social-message.mod-curator-invite,
  .social-message.mod-become-manager,
  .social-message.mod-studio-activity {
    background-color: hsl(163, 60%, 85%);
  }
  
  .social-message.mod-love-favorite {
    background-color: hsl(45, 90%, 95%);
  }
  
  .social-message.mod-love-project {
    background-color: hsl(350, 100%, 95%);
  }
  
  .social-message.mod-remix-project {
    background-color: hsl(260, 100%, 90%);
  }
  
  .social-message.mod-unread {
    background-color: hsl(100, 95%, 95%);
    box-shadow: 0 2px 3px -2px rgba(0, 200, 200, 80%);
    position: relative;
  }
}