 <!-- custom styling for all icons -->
  i.fas,
  i.fab {
    border: 1px solid red;
  }

  <!-- custom styling for specific icons -->
  .fa-fish {
    color: salmon;
  }

  .fa-frog {
    color: green;
  }

  .fa-user-ninja.vanished {
    opacity: 0.0;
  }

  .fa-facebook {
    color: rgb(59, 91, 152);
  }
  
  .fa-windows {
    color: rgb(29, 134, 200);
  }
  
  .fa-solar-panel {
    color: rgb(29, 134, 200);
  }
 
  .fa-car-battery {
    color: rgb(29, 134, 200);
  }
  
  .fa-charging-station {
    color: rgb(29, 134, 200);
  }

  .fa-calendar {
    color: rgb(29, 134, 200);
  }