wp-syntax-rettke serves as an example for the programmatic "Advanced Configuration" of GeSHi in Ryan McGeary's excellent WP-Syntax plugin.
Out of the box, WP-Syntax
colors code using the default GeSHi colors.
Per the authors advice in the 'Advanced Customization' section of
you can configure GeSHi yourself by handling the
hook and configuring it programmatically.
Since I wanted to do just that, I decided to publish a generic plugin for folks who wanted to configure GeSHi following this approach.