JSFiddle - React, Tailwind, and code Playground

HTML

<div class="block"></div>
<div class="block"></div>
<div class="block"></div>
<input type="button" value="get color" id="click"/>

CSS

div{height:100px;width:100px;border:2px solid black;}

JavaScript

$(document).ready(function() {
    var colors = ["red", "blue", "green", "purple"];
   var bodybgarrayno = Math.floor(Math.random() * colors.length);
                var selectedcolor = colors[bodybgarrayno];
                $(".block").css("background",selectedcolor);
            });