If a kitchen model is properly designed, you can change the aspect of its parts.
So, if a model is designed with components like cabinet body, front/door/drawer, handle, worktop, etc, than each of these parts can be changed. Use Furniture --> Modify furniture --> Materials.

It is not posible to change one aspect of multiple object in one go, e.g. you cannot change all fronts of cabinets from red to blue. (It is possible, however, to change multiple exactly identical objects in one go.)

H