JSFiddle - React, Tailwind, and code Playground

HTML

<div class="row">
    <div class="red">Red</div>
    <div class="red">Red</div>
    <div class="red">Target Me With CSS???</div>
    <div class="blue">Blue</div>
    <div class="blue">Blue</div>
    <div class="blue">Blue</div>
</div>

CSS

.row > div{
    display:inline-block;
    padding:10px;
}

.row .red{
    background-color:#770000;    
    color:#fff;
}

.row .last-red-class {
    background-color:#440000;    
    color:#fff;
    font-weight: bold;
}

.row .red:last-of-type{
    background-color:#FF0000;    
}

.row div:last-child{
    background-color:#0000BB;    
}

JavaScript

$(function() {
    $('.row .red').last().addClass('last-red-class');
});