JSFiddle - React, Tailwind, and code Playground

HTML

<div class=box></div>
<div class=box></div>
<div class=box></div>
<div class=box></div>
<div class=box></div>
<div class=box></div>
<div class=box></div>

CSS

.box {
    width: 100px;
    height: 100px;
    float: left;
    display: block;
}

JavaScript

var box = document.getElementsByClassName('box');
    div=0;
    setInterval(function(){
            box.item(div).style.backgroundColor = '#'+Math.floor(Math.random()*16777215).toString(16);
            div++;
            if(div>=box.length){
                div=0;
            }
        },2000);