There was a plug-in for Sketchup that did just that - try searching "Color by Slope". I haven't used it recently though. It paints surfaces according to their slopes. There is also a "Color by Height" variant. These might work for you.

Thanks for the models. Will be useful.

Thank you for these components. And thank you for reminding me to clean up and organize my own door components!

Similar thing happened to me once. I changed the units in the import dialogue to something much bigger and Skethcup was able to generate the faces succesfully. I scaled model back down once in Sketchup. The actual CAD file was in centimeters, but I imported it as meters I think. Give it a try.

Thanks. It's always a bore modelling those switches...