JSFiddle - React, Tailwind, and code Playground

HTML

<section>
<div class="someclass"></div>
<div id="someId"></div>
<div class="someotherclass"></div>
<div id="someotherId"></div>
<div class="someclass"></div>
<div id="someId"></div>
<div class="someotherclass"></div>   
</section>

CSS

div {
    width:50px;
    height:50px;
    background:black;
    margin:10px;
}

section > div:nth-child(3n+1) {
    background:red;
}