如何在使用Bootstrap的CSS类时改变表格单元格的背景颜色？

<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.0/dist/css/bootstrap.min.css">
<script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.0/dist/js/bootstrap.bundle.min.js"></script>

<table class="table">
  <tbody>
    <tr>
      <td class="bg-danger">单元格1</td>
      <td>单元格2</td>
    </tr>
    <tr>
      <td>单元格3</td>
      <td class="bg-danger">单元格4</td>
    </tr>
  </tbody>
</table>

<style>
  .bg-custom {
    background-color: blue;
  }
</style>

<td class="bg-custom">单元格内容</td>