different theme for different forms

I am trying to create directories of the Gravity Forms entries for different forms using the Gravity Forms Directory plugin. I have included a snippet in my theme’s function.php to change the default theme of the plugin (see below). However, I would like to show my different forms in different themes. Any idea on how I can modify the snippet to accomplish that?

<?php
// filter to change the look of form entries via GF Directory add-on

add_filter(‘kws_gf_tablesorter_theme’, ‘change_theme’);
function change_theme($form) {
return ‘grey’;
}

?>

https://wordpress.org/plugins/gravity-forms-addons/