How to display products of the same category on a single-product page?

I have problems to display a list of products of the same category in the mp_product.php template...

Basicaly what i want to do is:
<?php mp_list_products(true, true, 0, 3, "THE CURRENT CATEGORY", 'DESC'); ?>
Can i use a variable for the category string in mp_list_products?

Here is an example: The product category is 'modell-lienz'. I want to list all the other variations of colors of 'modell-lienz' after the product-content.
http://www.thomas-christoph.com/brugger/store/produkte/lienz-panna/

Thank you in advance...