JSFiddle - React, Tailwind, and code Playground

HTML

<table class="resultGridTable" cellspacing="0" id="detailContentPlaceholder_grdTransactions"
    style="border-collapse: collapse;">
    <tr class="first">
        <th scope="col">
            &nbsp;
        </th>
        <th colspan='4' class='tableHeaderColGroup'>
            Associate Transaction Info
        </th>
        <th colspan='5' class='tableHeaderColGroup'>
            Financial Transaction Info
        </th>
        <th colspan='2' class='tableHeaderColGroup'>
            Success Dates
        </th>
        <th colspan='2' class='tableHeaderColGroup'>
            Tracking Dates
        </th>
        <th colspan='1' class='tableHeaderColGroup'>
            Test
        </th>
        <th colspan='5' class='tableHeaderColGroup'>
            Transaction Info
        </th>
        <th colspan='2' class='tableHeaderColGroup'>
            Reference Amts
        </th>
        <th colspan='12' class='tableHeaderColGroup'>
            Daily Tax or Payroll Adjustments Info
        </th>
    </tr>
    <tr  class="second">
        <th>
            Line #
        </th>
        <th scope="col">
            EmpID
        </th>
        <th scope="col">
            Ref
        </th>
        <th scope="col">
            First&#160;Name
        </th>
        <th scope="col">
            Last&#160;Name
        </th>
        <th scope="col">
            Type
        </th>
        <th scope="col">
            App ID
        </th>
        <th scope="col">
            Batch ID
        </th>
        <th scope="col">
            Correlation&#160;ID
        </th>
        <th scope="col">
            Transaction ID
        </th>
        <th scope="col">
            Posted Date
        </th>
        <th scope="col">
            Completed Date
        </th>
        <th scope="col">
            Updated
        </th>
        <th scope="col">
            Rejected
        </th>
        <th scope="col">
            Yes/No
        </th>
        <th scope="col">
            Invoice ID
 ...

CSS

.first
{
    border: 1px solid red;
}
.second
{
    border: 1px solid orange;
}
.dataRow
{
    border: 1px solid blue;
}

td
{
    padding: 5px 5px 5px 5px;
}

th
{
    padding: 5px 5px 5px 5px;
}

JavaScript

var table = $('#detailContentPlaceholder_grdTransactions'),
    trs = table.find('tr'),
    headTr = table.find('.second'),
    empHeader = $($(headTr).children('th')[1]);

table.width(table.width() + 300);

empHeader.css('background-color', 'red');
empHeader.width(300);


#detailContentPlaceholder_grdTransactions > tbody > tr.second > th:nth-child(2)