<style>
  .first-half {
    background-color: var(--c1);
  }
  .second-half {
    background-color: var(--c6);
  }
</style>
<table>
  <caption>Revenue 2025</caption>
  <colgroup>
    <col span="2" class="first-half">
    <col span="2" class="second-half">
  </colgroup>

  <tr>
    <th>Q1</th>
    <th>Q2</th>
    <th>Q3</th>
    <th>Q4</th>
  </tr>
  <tr>
    <td>100</td>
    <td>40</td>
    <td>30</td>
    <td>400</td>
  </tr>
  <tr>
    <td>20</td>
    <td>10</td>
    <td>8</td>
    <td>100</td>
  </tr>
</table>