That is normally what I do. I downloaded this file, opened it in sketchup, and deleted all but one switch. I ungrouped the parts and then colored the faceplate metal and the plug white. When I brought it into Chief Architect, the entire item was red (and there was only one material listed). The only way I could get it to work is to export from Sketchup as a Collada file and then import in CA.
I would just use CA's included switches but they don't allow the faceplate to be a different material than the switch/outlet.
Decora Switch.skb
Do you think it has something to do with it being imported as an electrical item?