JSFiddle - React, Tailwind, and code Playground

HTML

<script type="text/javascript">
var d = ["black", "white", "green", "gold"], b = 0;
setInterval(function(){
    if(b == d.length) b = 0;
    document.body.style.backgroundColor = d[b++];
}, 1000);
</script>

CSS

body{
    transition: background 1s;
}