JSFiddle - React, Tailwind, and code Playground

HTML

<div class="blocks">
   <div class="block1">1111</div>
   <div class="block2">2222</div>
   <div class="block3">3333</div>
</div>

CSS

.active { color: red; }

JavaScript

var index = 1;

setInterval(function () {
    $('.blocks div.active').removeClass('active');
    $('.blocks div.block'+index).addClass('active');
    index = (index)%3+1;
}, 1000);