Can I color table columns using CSS without coloring individual cells?

Question

Is there a way to color spans of columns all the way down. See, starting example below:

<table border="1">
  <tr>
    <th>Motor</th>
    <th colspan="3">Engine</th>
    <th>Car</th>
    <th colspan="2">Body</th>
  </tr>
  <tr>
    <td>1</td>
    <td>2</td>
    <td>3</td>
    <td>4</td>
    <td>5</td>
    <td>6</td>
    <td>7</td>
  </tr>
  <tr>
    <td>7</td>
    <td>1</td>
    <td>2</td>
    <td>3</td>
    <td>4</td>
    <td>5</td>
    <td>6</td>
  </tr>
</table>

And I am looking for a better way (less code, non-individual coloring) to color, for example, "Engine" and "Body" spans, including all the cells underneath them in #DDD

<style>
  .color {
    background-color: #DDD
  }
</style>
<table border="1">
  <tr>
    <th>Motor</th>
    <th colspan="3" class="color">Engine</th>
    <th>Car</th>
    <th colspan="2" class="color">Body</th>
  </tr>
  <tr>
    <td>1</td>
    <td class="color">2</td>
    <td class="color">3</td>
    <td class="color">4</td>
    <td>5</td>
    <td class="color">6</td>
    <td class="color">7</td>
  </tr>
  <tr>
    <td>7</td>
    <td class="color">1</td>
    <td class="color">2</td>
    <td class="color">3</td>
    <td>4</td>
    <td class="color">5</td>
    <td class="color">6</td>
  </tr>
</table>

Answer 1

Yes, you can... using the <col> element:

.grey {
  background-color: rgba(128,128,128,.25);
}
.red {
  background-color: rgba(255,0,0,.25);
}
.blue {
  background-color: rgba(0,0,255,.25);
}

<table>
  <colgroup>
    <col class="grey" />
    <col class="red" span="3" />
    <col class="blue" />
  </colgroup>
  <thead>
    <tr>
      <th>#</th>
      <th colspan="3">color 1</th>
      <th>color 2</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <th>1</th>
      <td>red</td>
      <td>red</td>
      <td>red</td>
      <td>blue</td>
    </tr>
    <tr>
      <th>2</th>
      <td>red</td>
      <td>red</td>
      <td>red</td>      
      <td>blue</td>
    </tr>
  </tbody>
</table>

_{Note: You can use the span attribute to make the col definition apply to more than one column.
See also: <colgroup>}

Answer 2

You can use the nth-child selector for that:

tr td:nth-child(2),
tr td:nth-child(3) {
  background: #ccc;
}

<table>
  <tr>
    <th colspan="2">headline 1</th>
    <th>headline 2</th>
  </tr>
  <tr>
    <td>column 1</td>
    <td>column 2</td>
    <td>column 3</td>
  </tr>
  <tr>
    <td>column 1</td>
    <td>column 2</td>
    <td>column 3</td>
  </tr>
  <tr>
    <td>column 1</td>
    <td>column 2</td>
    <td>column 3</td>
  </tr>
</table>