JSFiddle - React, Tailwind, and code Playground

HTML

<aside class="col2">
    <div class="infobox teal">1</div>
    <div class="infobox mediumbrown">2</div>
    <div class="quotebox">3</div>
    <div class="quotebox">4</div>
</aside>

JavaScript

$(function() {
       $("aside.col2 div:not('.quotebox'):last").css("color","red");
    });