JSFiddle - React, Tailwind, and code Playground

HTML

<div class="fieldset"></div>
<div class="fieldset"></div>
<div class="fieldset"></div>
<div class="fieldset"></div>
<div class="fieldset"></div>
<div class="fieldset"></div>
<div class="fieldset"></div>

CSS

.fieldset{
  border: 1px solid #000;
  width: 50px;
  height: 50px;
}
.fieldset:nth-child(2){
  background: red;
}
.fieldset:nth-child(6){
  background: blue;
}