JSFiddle - React, Tailwind, and code Playground

HTML

<div class="panel panel-custom-horrible-red">
  <div class="panel-heading">
    <h3 class="panel-title">Panel title</h3>
  </div>
  <div class="panel-body">
    Panel content
  </div>
</div>

CSS

@import url('//maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css');
.panel-custom-horrible-red {
    border-color: #ff0000;
}
.panel-custom-horrible-red > .panel-heading {
    background: #ff0000; 
    color: #ffffff;
    border-color: #ff0000;
}