JSFiddle - React, Tailwind, and code Playground

HTML

<div class="trow">
  <span class="group">1</span>
  <span class="group">2</span>
  <span class="group">3</span>
  <span>4</span>
  <span>5</span>
  <span>6</span>
</div>

CSS

.trow span.group:last-child{
  background:blue;
  color:#fff;
}