This is more of styling HTML code to use a manual accordion or 1 off click / reveal content. Most useful in Drupal Views instead of some accordion module. 

<div  class="gt-details-summary">  
<details class="bg-gt-black">
    <summary class="bg-gt-pi-mile">TITLE HERE</summary>
   <article class="bg-white">
       content here
    </article>
</details>
</div>

Needs gt-detail-summary class wrapper, details, summary & article for the content. Then you color it as you see fit. this is just the wire frame.