JSFiddle - React, Tailwind, and code Playground

HTML

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

CSS

:root {
    -webkit-var-count: 5;
}

li {
    width:100px;
    height:100px;
    background-color:blue;
    display:inline-block;
    list-style:none;
}


ul li:nth-child(4) {
    background-color:red;
}

ul li:nth-child(-webkit-var(count)) {
    background-color:black;
}