JSFiddle - React, Tailwind, and code Playground

HTML

<table class="pdftable2" id="j_info" border="1">
        <tr>
            <th>Group Name</th> 
            <th>Yes</th>    
            <th>NA</th>
            <th>No</th>
        </tr>
        <tr>
            <td colspan="4">Sub Group name</td> 
        </tr>
        <tr>
            <td>
                Phasellus sagittis tristique augue
            </td>
            <td></td>
            <td>X</td>
            <td></td>
        </tr>
    </table>

CSS

.highlight
{
  background-color: green;
}

JavaScript

$(document).ready(function()
{
  $('tr').find('td').eq(0).addClass('highlight');
});