Any colour can be added to the border by using the following border-color classes that are available in bootstrap. If you want any other cutomized color, then you can set it manually using the CSS attribute.
Example-1
<!DOCTYPE html> <html> <head> <title>Bootstrap Example</title> <!-- Link Bootstrap CSS --> <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css"> <!-- Link Bootstrap JS and JQuery --> <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.3/umd/popper.min.js"></script> <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/js/bootstrap.min.js"></script> <style> /* CSS style for Boxes */ span { display: inline-block; width: 70px; height: 70px; margin: 6px; background-color: #DCDCDC; } </style> </head> <body> <div class="container"> <h2>Borders</h2> <p>Color Border:</p> <span class="border border-primary"></span> <span class="border border-secondary"></span> <span class="border border-success"></span> <span class="border border-danger"></span> <span class="border border-warning"></span> <span class="border border-info"></span> <span class="border border-light"></span> <span class="border border-dark"></span> </div> </body> </html>
<!DOCTYPE html> <html> <head> <title>Bootstrap Example</title> <!-- Link Bootstrap CSS --> <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css"> <!-- Link Bootstrap JS and JQuery --> <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.3/umd/popper.min.js"></script> <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/js/bootstrap.min.js"></script> <style> /* CSS Style for Boxes */ span { display: inline-block; width: 70px; height: 70px; margin: 6px; background-color: #DCDCDC; } </style> </head> <body> <div class="container"> <h2>Border Radius</h2> <!-- Below classes are used to add radius to the borders --> <span class="rounded"></span> <span class="rounded-top"></span> <span class="rounded-right"></span> <span class="rounded-bottom"></span> <span class="rounded-left"></span> <span class="rounded-circle"></span> <span class="rounded-0"></span> </div> </body> </html>