There are some Nokia Lumia 900 users who are reporting that the display screens of their handsets are turning purple.
image from Google Images
They said that they would only see this when you put the brightness settings of the phones backlight to low (which I do with all of my phones – lesser battery consumption).
Good thing Nokia has already acknowledged the problem and said that they’re now working for a “bug fix”. However the release date of the fix is still unknown.