JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html lang="en" >
<head>
  <meta charset="UTF-8">
  <title></title>
  <meta charset="UTF-8">
  <title></title>
  <meta name="viewport" content="width=device-width, initial-scale=1">  
  <link rel="stylesheet" type="text/css" href="https://cdn.datatables.net/v/dt/dt-1.10.23/datatables.min.css"/>
  
<script type="text/javascript" src="https://code.jquery.com/jquery-3.5.1.js"></script>
  
<script type="text/javascript" src="https://cdn.datatables.net/v/dt/dt-1.10.23/datatables.min.js"></script>
  
</head>
<body>
<!-- partial:index.partial.html -->
<table id="example" class="display" cellspacing="0" width="100%" border=1>

<br>
<br>
<br>
<br>
  <thead>
     <tr>
      <th rowspan="1"></th>
      <th colspan="7">Week 5</th>
      <th colspan="7">Week 6</th>
      <th colspan="7">Week 7</th>
      <th colspan="7">Week 8</th>
    </tr>

    <tr>
      <th rowspan="2">Name</th>
      <th colspan="1">Mo</th>
      <th colspan="1">Tu</th>
      <th colspan="1">We</th>
      <th colspan="1">Th</th>
      <th colspan="1">Fr</th>
      <th class="weekend" colspan="1">Sa</th>
      <th class="weekend" colspan="1">Su</th>
      <th colspan="1">Mo</th>
      <th colspan="1">Tu</th>
      <th colspan="1">We</th>
      <th colspan="1">Th</th>
      <th colspan="1">Fr</th>
      <th colspan="1">Sa</th>
      <th colspan="1">Su</th>
      <th colspan="1">Mo</th>
      <th colspan="1">Tu</th>
      <th colspan="1">We</th>
      <th colspan="1">Th</th>
      <th colspan="1">Fr</th>
      <th colspan="1">Sa</th>
      <th colspan="1">Su</th>
      <th colspan="1">Mo</th>
      <th colspan="1">Tu</th>
      <th colspan="1">We</th>
      <th colspan="1">Th</th>
      <th colspan="1">Fr</th>
      <th colspan="1">Sa</th>
      <th colspan="1">Su</th>
    </tr>
	
    <tr>
      
      <th>1</th>
      <th>2</th>
      <th>3</th>
      <th>4</th>
      <th>5</th>
      <th>6</th>
      <th>7</th>
      <th>8</th>
      <th>9</th>
      <th>10</th>
      <th>11</th>
     ...

CSS

thead tr:nth-child(1) {
    line-height: 54px;
}

thead tr:nth-child(2) {
    line-height: 30px;
}

 th.weekend  {
     background-color: red;
 }

JavaScript

var table = $('#example').DataTable();