JSFiddle - React, Tailwind, and code Playground

HTML

<div id="wrapper">
    <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

#wrapper {
    width: 240px;
    border: 1px solid #999;
    overflow: hidden;
}

#wrapper div {
    width: 60px;
    height: 60px;
    float: left;
    background-color: #fff;
}

#wrapper .dark {
    background-color: #f5f5f5;
}

JavaScript

$("#wrapper > :nth-child(8n+1), #wrapper > :nth-child(8n+3), #wrapper > :nth-child(8n+6), #wrapper > :nth-child(8n+8)").addClass('dark');