So, I found an article at Ignored By Dinosaurs describing how to add syntax highlighting to php-markdown code blocks...
I first downloaded the prism.js and prism.css, and placed each in the respective folders in my theme.
I then added a reference to them in my layout.html.php (heavily modified doks theme):
<link rel="stylesheet" href="<?php echo theme_path();?>css/prism.css">
<script src="<?php echo theme_path();?>js/prism.js"></script>
I then added "language-" to MarkdownExtra.php:
/**
* Optional class prefix for fenced code block.
* @var string
*/
public $code_class_prefix = "language-";
Cleared the cache, and 🔥BOOM🔥 ;)
I have not, yet, figured-out how to correctly modify the colouring of the highlighting, but what-is surely beats the default B&W
So; it's so:
Prism Themes ;)