JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
    <li>Item</li>
    <li>Item</li>
    <li>Item</li>
    <li>Item</li>
    <li>Item</li>
    <li>Item</li>
    <li>Item</li>
    <li>Item</li>
</ul>

CSS

ul li:nth-child(2n){
    background-color: blue;
}

ul li:nth-child(3n){
    background-color: red;
}