Ah, that color may not exist in MD so you will have to write that in to your stylesheets for each color like in my example above.
To keep the stylesheet light I haven't included many color names, so you can add the colors you need only. Sometimes I use inline styles while on the fly, but it's always best to establish your colors in CSS.
You can make as many custom colors as you want like so in your child theme style.css:
.badge.green { background-color: green; }
.badge.pink { background-color: pink; }
Here's the inline way to do it if you're ever feeling lazy:
Text goes here and <span class="badge" style="background:blue;">badge</span> goes here.