@keyframes rainbow {
  0% { color: #ff0000; }
  10% { color: #ff6600; }
  20% { color: #ffff00; }
  30% { color: #66FF00; }
  40% { color: #00ff00; }
  50% { color: #00ffff; }
  60% { color: #0000ff; }
  70% { color: #6666FF; }
  80% { color: #6600ff; }
  90% { color: #6600ff; }
  100% { color: #ff00ff; }
}