Unless someone can write a Python Script that could automate that procedure between different types of clothing there isn't an easy way, and without specifying which Poser version and render engine you are using, the process may be trickier.  Everything will happen in the Material Room, desaturating parts of your scene and applying a grayscale tint while other parts remain untouched.  This will make the process very tedious if you have many Material zones to change.