ReorMadrid

To use it, you must use the [code] shortcode like this:
PHP Code Example:
[easycode] 
< ? php 
e cho “Hi, world!”; 
 ? > 
[/easycode]
In the admin menu, you have options to change the background colors, button colors, language and more.

Easy Code Highlighter

Displays code with syntax highlighting using Prism.js, real line numbering, and a copy button.

rtCamp

Rahul Bansal

Joshua Abenazer

Harish Chaudhari

<ol>
<li>Uses <a href="http://softwaremaniacs.org/soft/highlight/en/" rel="nofollow ugc">highlight.js</a>.</li>
<li>26 themes included.</li>
<li>55 languages supported (54 from highlight.js + 1 for nginx commands).</li>
<li>Auto-detects language.</li>
<li>Super-optimised, only loads js for the language.</li>
<li>Adds buttons to tinyMCE for ease of adding code blocks.</li>
<li>Optimised code with minimal overheads.</li>
<li>All code on <a href="https://github.com/rtCamp/rtsyntax" rel="nofollow ugc">Github</a>.</li>
</ol>

rtSyntax

A no-fuss, lightweight, fast and optimised syntax highlighter for WordPress

Easy Code Highlighter vs rtSyntax