To add a blue left border to a list in CSS, you can try to run the following code −
Example
<!DOCTYPE html>
<html>
<head>
<style>
ul {
border-left: 3px solid blue;
background-color: #gray;
}
</style>
</head>
<body>
<p>Countries</p>
<ul>
<li>India</li>
<li>US</li>
<li>Australia</li>
</ul>
</body>
</html>Output
