JSFiddle - React, Tailwind, and code Playground

HTML

<div class="green" id="ready">R</div>
<div class="orange" id="steady">S</div>
<div class="red" id="go">G</div>

CSS

.active{
    background:red;
}

JavaScript

var lights=$('#ready, #steady, #go');

jQuery.each(lights, function(i) { 
    var el=$(this);
    setTimeout(function() { 
        el.addClass('active');
    }, i * 3000); 
});