You have to define each material/color you are using. If you change the image used by a material, everything that uses that material will use the new image when they are opened.
The material definition (name, deminisions, color, cost, etc) is contained in an Access database while each object (cabinet, display panel, display board, display cube) file contains a reference to the database definition. If you change it, it changes for everything.
I think a better solution to your problem is on that has already been discussed.
That would be the ability to "Paint" Textures to cabinets.
It is just an expansion of the Texture match already available in eCabinets.
you could change any material to any color and that would be saved with the job so one job could be white and the other brown using the same material.