body {
  animation: rotate-bg-color 10s infinite;
}

@keyframes rotate-bg-color {
  0% {
    background-color: steelblue;
  }
  10% {
    background-color: red;
  }
  20% {
    background-color: orange;
  }
  30% {
    background-color: yellow;
  }
  40% {
    background-color: green;
  }
  50% {
    background-color: blue;
  }
  60% {
    background-color: indigo;
  }
  70% {
    background-color: violet;
  }
  80% {
    background-color: pink;
  }
  90% {
    background-color: brown;
  }
  100% {
    background-color: black;
  }
}