Tryit Editor v2.9

Edit This Code:
<!DOCTYPE html>
<html>
<head>
<style>
table, th, td {
    border: 1px solid black;
}
</style>
</head>
<body>

<table>
  <colgroup>
    <col id="myCol">
    <col style="background-color:yellow">
  </colgroup>
  <tr>
    <th>ISBN</th>
    <th>Title</th>
    <th>Price</th>
  </tr>
  <tr>
    <td>3476896</td>
    <td>My first HTML</td>
    <td>$53</td>
  </tr>
  <tr>
    <td>5869207</td>
    <td>My first CSS</td>
    <td>$49</td>
  </tr>
</table>

<p>Click the button to set the background color of the first two columns to red.</p>

<p id="demo"></p>

<button onclick="myFunction()">Try it</button>

<script>
function myFunction() {
    document.getElementById("myCol").span = "2";
    document.getElementById("myCol").style.backgroundColor = "red";
}
</script>

</body>
</html>