WordPress – Add user roles to body class

wp-user-role-body-class.php

<?php
function tk_add_user_role_to_body_classes($classes)
{
    global $current_user;

    foreach ($current_user->roles as $user_role) {
        if (is_admin()) {
            $classes .= ' role-' . $user_role;
        } else {
            $classes[] = 'role-' . $user_role;
        }
    }

    return $classes;
}

add_filter('body_class', 'tk_add_user_role_to_body_classes', 100);
add_filter('admin_body_class', 'tk_add_user_role_to_body_classes', 100);