要将浅灰色背景色添加到Bootstrap中的卡，请使用bg-light上下文类和卡类。
要设置浅灰色背景，请将其添加到<div>类中-
<div class="card bg-light text-dark"> <div class="card-body">Reduce size of images</div> </div>
您可以尝试运行以下代码以在Bootstrap 4中为卡添加亮灰色背景色-
<!DOCTYPE html> <html lang="en"> <head> <title>Bootstrap Example</title> <meta charset="utf-8"> <meta name="viewport" content="width=device-width, initial-scale=1"> <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.0/css/bootstrap.min.css"> <script src="https://cdn.staticfile.org/jquery/3.3.1/jquery.min.js"></script> <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.0/js/bootstrap.min.js"></script> </head> <body> <div class="container"> <h2>Optimization</h2> <div class="card bg-light text-dark"> <div class="card-body">Reduce size of images</div> </div> <div class="card bg-light text-dark"> <div class="card-body">Clear Cache</div> </div> <div class="card bg-light text-dark"> <div class="card-body">Use CDN</div> </div> </div> </body> </html>