.red {background-color : red }
div.t1 p { background-color : lime }

<div class="t1">
  <p class="red">This paragraph should have a green background</p>
  <table>
    <tbody>
      <tr>
<td>
<p class="red">This paragraph should have a green background</p>
</td>
</tr>
    </tbody>
  </table>
</div>
<table>
<tbody>
<tr>
<td>
<p>This paragraph should NOT have a green background</p>
</td>
</tr>
</tbody>
</table>