Bootstrap class: .thead-dark

<table class="table">
  <thead class="thead-dark">
    <tr>
      <th>#</th>
      <th>First Name</th>
      <th>Last Name</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <th scope="row">1</th>
      <td>Mark</td>
      <td>Otto</td>
    </tr>
    <tr>
      <th scope="row">2</th>
      <td>Jacob</td>
      <td>Thornton</td>
    </tr>
  </tbody>
</table>

Preview

# First Name Last Name
1 Mark Otto
2 Jacob Thornton

Sass source

/* _tables.scss:115 */
.thead-dark {
  th {
    color: $table-dark-color;
    background-color: $table-dark-bg;
    border-color: $table-dark-border-color;
  }
}

Uses variables

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/* _tables.scss:115 */
$table-dark-color
$table-dark-bg
$table-dark-border-color

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