css animation
<style> .my-element { width: 100%; height: 100%; animation: tween-color 5s infinite; } @keyframes tween-color { 0% { background-color: red; } 50% { background-color: green; } 100% { background-color: red; } } html, body { height: 100%; } <style> <body> <div class="my-element"></div> </body>