JSFiddle - React, Tailwind, and code Playground

HTML

<div> color uno </div>
<div> color dos </div>
<div> color tres </div>
<div> color uno </div>
<div> color dos </div>
<div> color tres </div>
<div> color uno </div>
<div> color dos </div>
<div> color tres </div>
<div> color uno </div>
<div> color dos </div>
<div> color tres </div>

CSS

div:nth-child(3n+1) { background:#00ff00; }
div:nth-child(3n+2) { background:#555 }
div:nth-child(3n+3) { background: #ff00cc; }