In iOS 6 the lack of color is normal. It's still capable of displaying color but the status bar changes in the new OS means the color versions of the default icons aren't being used. (An exception would be the superman logo)
That's because each icon actually has a folder which several versions of the icon depending on the type of status bar being used, so that they blend in with the theme. And since there's one type of status bar that no longer exists, the icons associated with it is never being displayed. Same reason why we don't see blue signal bars or green battery icons anymore.
Reason why superman logo shows color is that all versions of that logo are in color so no matter what status bar is used, they are all the same.
You can actually get the color versions to show by renaming the files so that the color icons get picked despite the black and white status bar.