JSFiddle - React, Tailwind, and code Playground

HTML

<div id="content">
    <div class="block">Block-1</div>
</div>

CSS

#content .block{
    background:green;
}

JavaScript

$(function(){
    var c = $('#content'), l = c.find('.block').length;
    setInterval(function(){
        var lOld = l;
        if(c.find('.block').length > lOld) {
            l = c.find('.block').length;
            c.find('.block').css({ "background-color" : bg[l] });
        }
    }, 100);
    
    // For the example
    var bg = [ '#FFFFFF', '#FF0000', '#0000FF', '#00CCF1', '#DD00F1'];
    var intVal = setInterval(function(){
        var b = $('<div/>', { 'class':'block', 'text':'Block-' + (++c.find('.block').length) });
        $('#content').append(b);
        if(c.find('.block').length >= (bg.length-1)) clearInterval(intVal);
    }, 3000);
});