向Bootstrap 4卡添加浅灰色背景色
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Bootstrap4中为卡添加亮灰色背景色-
示例
<!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>