The Syntax Highlighting included with the Documentation app can be found at Google Code.
To highlight your code, you'll need to put your code snippets in <pre class="prettyprint">...</pre>; or <code class="prettyprint">...</code>
and it will automatically be pretty printed.
Further you can make the syntax HTML 5 compliant by wrapping your code in <pre class="prettyprint"><code class="language-php">...</code></pre>
If you are not using the Documentation app, but want to use the Syntax Highlighting anyway, you'll have to include the Syntax Highlighting in your app template. You'll need to add the following code snippets.
// include syntaxhighlighter
$this->app->document->addScript($this->template->resource.'libraries/prettify/prettify.js');
$this->app->document->addStylesheet($this->template->resource.'libraries/prettify/prettify.css');
<script type="text/javascript">;
jQuery(function($) { prettyPrint(); });
</script>