JSFiddle - React, Tailwind, and code Playground

HTML

<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>
<div></div>

CSS

div {
  float: left;
  width: 50px;
  height: 50px;
  background: grey;
  border: 1px solid black; 
}

div:nth-child(odd) {
    background: red;
}

div:nth-child(even) {
    background: blue;
}

div:nth-child(3n) {
    background: yellow;
}