If you even need a nice box around something with colour, use this.

<div class="box-container emerald">
  <h1>Lorem ipsum</h1>
  <p>Lorem ipsum dolor sit amet, consectetur...</p>
</div>

Preview

Lorem ipsum

Lorem ipsum dolor sit amet, consectetur...

Message warning

If you need to showcase a message at top, you can use this.

<div class="box-container alizarin-flat message">
  <a class="close">×</a>
  <p>This website is still under progress</p>
</div>

Preview

×

This website is still under progress

See a live preview here