body {
  background: linear-gradient(45deg, #fa8bff 0%, #2bd2ff 50%, #2bff88 100%) 0 0 / 200% 100% repeat;
  animation: animation-bg-gradient 5s infinite alternate;
}

@keyframes animation-bg-gradient {
  0% {
    background-position: 0 0;
  }
  100% {
    background-position: 100% 0;
  }
}

External CSS

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External JavaScript

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