Drupal 8, show attributes from order item.

commerce-order-receipt.html.twig

               {% for attribute_data in order_item.getPurchasedEntity().getAttributeValues() %}
                                                        <tr>
                                                          <td align="left" valign="top" class="product-attr" style="color: #000000; font-family: 'Nunito Sans', sans-serif; font-weight: 400; font-size: 14px; line-height: 22px;">{{ attribute_data.getAttribute().label() }}:  {{ attribute_data.label() }}</td>
                                                        </tr>
                                                      {% endfor %}