If you are not a coder then you will have to get someone to create the mod for you either by hireing a 3rd party developer or contact x-cart direct.
if you want 3rd party the I cant recommened Carrie at BCSE enough.
I presume this is the sort of thing you want but with normal drop down boxes and changes on thumbnail rather than fabric swatch
http://www.justhom.com/product.php?productid=21&cat=7&page=1