If you're a developer, you shouldn't have problems to read the Home.xml entry stored in a SH3D file (a SH3D file is just a ZIP file), then keep the information you want by parsing it with your own parser or transform it with a XSLT file.
The DTD of Home.xml entry is available at https://www.sweethome3d.com/SweetHome3D.dtd and you'll see that furniture materials, textures and colors can be easily be identified. I would suggest to create a SH3D file using different type of colors / textures on walls and rooms, then look at its Home.xml entry to find the information you want.