body {
  background-color: #e74c3c;
  animation: bg-color 10s infinite;
}
@keyframes bg-color {
  0% { background-color: #e74c3c; }
  20% { background-color: #f1c40f; }
  40% { background-color: #1abc9c; }
  60% { background-color: #3498db; }
  80% { background-color: #9b59b6; }
  100% { background-color: #e74c3c; }
}

p {
  font-family: Meiryo, "Hiragino Kaku Gothic Pro W3",sans-serif;
  text-align: center;
  margin-top: 150px;
  color: #fff;
}