JSFiddle - React, Tailwind, and code Playground

HTML

<table>
    <colgroup id="colgrp0"><col/><col/></colgroup>
    <colgroup id="colgrp1"><col/><col/></colgroup>
  <thead>
    <tr><th>Col A1</th><th>Col A2</th><th>Col B1</th><th>Col B2</th></tr>
  </thead>
 <tbody>
    <tr><td>A1</td><td>A2</td><td>B1</td><td>B2</td></tr>
 </tbody>
</table>

CSS

table
{    
   border-collapse: collapse;
   border: 1px solid blue;

}

#colgrp0
{
    background-color: #fed;
}

#colgrp1
{
    background-color: #def;
    border-left: 20px solid #fff;
}