dark class bootstrap code example

Example 1: bootstrap 4 bg

<div class="p-3 mb-2 bg-gradient-primary text-white">.bg-gradient-primary</div>
<div class="p-3 mb-2 bg-gradient-secondary text-white">.bg-gradient-secondary</div>
<div class="p-3 mb-2 bg-gradient-success text-white">.bg-gradient-success</div>
<div class="p-3 mb-2 bg-gradient-danger text-white">.bg-gradient-danger</div>
<div class="p-3 mb-2 bg-gradient-warning text-dark">.bg-gradient-warning</div>
<div class="p-3 mb-2 bg-gradient-info text-white">.bg-gradient-info</div>
<div class="p-3 mb-2 bg-gradient-light text-dark">.bg-gradient-light</div>
<div class="p-3 mb-2 bg-gradient-dark text-white">.bg-gradient-dark</div>

Example 2: bootstrap color a div

use something like :
<div class="container alert alert-success">
   <div class="row">
      <div class="col">I'm your content inside the grid!</div>
   </div>
</div>