[ Genesis ] Add body class based on category slug

functions.php

//* Add new body class based on post category
add_filter('body_class', 'wc_category_class_single');
function wc_category_class_single($classes){
 
global $post;
 
if(is_single()) {
    $category = get_the_category($post->ID);
    $slug = $category[0]->slug;
    $classes[] = 'post-category-'.$slug;
    }
 
    return $classes;
}