get_the_category_data.txt

WP_Term::__set_state(array(
     'term_id' => 24,
     'name' => 'Foo Parent',
     'slug' => 'foo-parent',
     'term_group' => 0,
     'term_taxonomy_id' => 24,
     'taxonomy' => 'category',
     'description' => '',
     'parent' => 0,
     'count' => 1,
     'filter' => 'raw',
     'cat_ID' => 24,
     'category_count' => 1,
     'category_description' => '',
     'cat_name' => 'Foo Parent',
     'category_nicename' => 'foo-parent',
     'category_parent' => 0,
  )),

get_the_category_experiment.php

<?php
// Experiment with get_the_category() to see the information it returns.
add_filter( 'the_content', 'append_get_the_category' );
function append_get_the_category( $content ) {
	if ( !is_single() ) return $content;

	$post_categories = get_the_category();
	
	return $content . '<pre>' . var_export( $post_categories, true ) . '</pre>';
}

post_categories_with_css_classes.php

<?php
/*
Plugin Name: Add CSS classes to post categories list
Plugin URI: https://www.facebook.com/groups/genesiswp/permalink/1907687709282417/
Description: Use get_the_category() instead of get_the_category_list() to add CSS classes to each category.
Author: Damien Carbery
Version: 0.1
*/


// Change post meta shortcodes to a custom shortcode.
// Maybe I should replace the 'post_categories' shortcode and with my code.
add_filter( 'genesis_post_meta', 'dcwd_change_post_meta_shortcode' );
function dcwd_change_post_meta_shortcode( $post_meta ) {
	return '[post_categories_with_classes] [post_tags]';
}


// Return the list of post categories with CSS classes for styling.
add_shortcode( 'post_categories_with_classes', 'dcwd_get_the_category_with_classes' );
function dcwd_get_the_category_with_classes( $atts ) {
	if ( ! is_object_in_taxonomy( get_post_type(), 'category' ) ) {
		return '';
	}

	$defaults = array(
		'sep'    => ', ',
		'before' => __( 'Filed Under: ', 'genesis' ),
		'after'  => '',
	);

	$atts = shortcode_atts( $defaults, $atts, 'post_categories' );
	
	$post_categories = get_the_category();
	
	// Do nothing if there are no categories.
	if ( ! $post_categories ) {
		return '';
	} 	

	$categories = array();
	foreach ( $post_categories as $category ) {
		$cat_classes = array();
		$cat_classes[] = 'cat';
		$cat_classes[] = 'cat-' . $category->slug;
		if ( 0 == $category->parent ) {
			$cat_classes[] = 'cat-parent';
		}
		else {
			$cat_classes[] = 'cat-child';
		}
		
		// TODO: Consider filtering this.
		$categories[] = sprintf( '<a href="%s" class="%s">%s</a>', esc_url( get_category_link( $category->term_id ) ), implode( ' ', $cat_classes ), $category->name );
	}
	
	if ( genesis_html5() ) {
		$output = sprintf( '<span %s>', genesis_attr( 'entry-categories' ) ) . $atts['before'] . implode( ' ', $categories ) . $atts['after'] . '</span>';
	} else {
		$output = '<span class="categories">' . $atts['before'] . implode( ' ', $categories ) . $atts['after'] . '</span>';
	}
	
	return '<style>.entry-categories .cat-parent { text-transform: uppercase; } .entry-categories .cat-child { font-style: italic; }</style>' . $output;
}