Change background colour of panel heading when toggled in Bootstrap collapsible panel group

I am trying to create a collapsible panel group using Bootstrap, and I would like the panel heading to change background colour when the panel group is not collapsed (one colour for collapsed panel group, one for unwrapped). I have tried using the :active selector, but this changes the colour only when clicked, it does not persist longer:

 <div class="panel-group">
  <div class="panel panel-default">
    <div class="panel-heading">
      <a data-toggle="collapse" class="panel-title" href="#collapse1">Title</a>
    </div>
    <div id="collapse1" class="panel-collapse collapse">
      <ul class="list-group">
        <li class="list-group-item">item 1</li>
        <li class="list-group-item">item 2</li>
      </ul> 
    </div>
  </div>
</div>

.panel-heading a:active {
  background: red;
}

https://jsfiddle.net/s625dgty/

I would appreciate any suggestions.

Solution

Use .active class instead of :active pseudo-class which only lasts as long as the user keeps their mouse-button (or pointing device equivalent) down. Target the link's parent .panel-header instead:

$('.panel-heading').on('click', function(e) {
  $(this).toggleClass('active');
});

The CSS has been modified to override .panel-heading with higher specificity by doubling the class:

.panel-heading.panel-heading {...

Some Bootstrap classes cannot be overridden by cascading priority, just double up on the target class as shown above -- do not use !important

Also, place <link> in the <head>. Place <script> before the closing </body> tag. See Demo.

Demo

.panel-heading.panel-heading.active {
  background: red;
}

.panel-title {
  display: inline-block;
  width: 100%;
}

.panel-heading.panel-heading.active .panel-title {
  color: white;
  font-weight: 900;
}

<!DOCTYPE html>
<html>

<head>
  <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.4.1/css/bootstrap.min.css">
</head>

<body>
  <div class="panel-group">
    <div class="panel panel-default">
      <div class="panel-heading">
        <a data-toggle="collapse" class="panel-title" href="#collapse1">Title</a>
      </div>
      <div id="collapse1" class="panel-collapse collapse">
        <ul class="list-group">
          <li class="list-group-item">item 1</li>
          <li class="list-group-item">item 2</li>
        </ul>
      </div>
    </div>
  </div>

  <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>
  <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.4.1/js/bootstrap.min.js"></script>
  <script>
    $('.panel-heading').on('click', function(e) {
      $(this).toggleClass('active');
    });
  </script>
</body>

</html>