JSFiddle - React, Tailwind, and code Playground

HTML

<main></main>

CSS

main {
  width: 150px;
  height: 100px;
  animation: 2s linear alternate infinite colouring;
}

@keyframes colouring {
  from {
    background-color: blue;
  }
  to {
    background-color: red;
  }
}