The 512ke change to Platinum at some time during 1987, at least internationally. In the US, that has not been verified. The Platinum 512Ke used the Mac Plus front case bezel. ( http://macdownunder.no-ip.info/Platinum512ke/ ) from this thread: http://68kmla.org/forums/viewtopic.php?t=334&start=50
I think you meant to say: The Apple IIe became Platinum in January 87.
The //c was NEVER "white". It was a creamy off-white which colour Apple called "Fog" with distinctly beige-coloured accents. All Snow White products were only released in Fog until the change to Platinum (which includes the ImageWriter II). In 1986 at the same time as the introduction of the IIGS, it is reported by numerous sources that with the RAM expansion ROM the IIc also changed to Platinum. Apple seems to support this in several technical articles by referring to it as the "Platinum" IIc, NOT the IIc Plus. Because of yellowing and differences in lighting in pictures, I have never seen a definitive picture or confirmation of the Platinum IIc, but it appears to have existed.
Scott, thanks for pointing out equill's error about the IIci, I read it as an Apple II rather than a Mac II ... the IIci MOST DEFINITELY was Platinum. NO Macintosh after the Plus was ever intentionally Apple beige. Actually more universally, NO NEW APPLE PRODUCT after 1986 was ever intentionally beige.