Steps to reproduce:
1. Place down any any non-black banner
2. Stand on the banner and run the command:
/clone ~ ~ ~ ~ ~ ~ ~ ~ ~1
3. The new banner will appear black, though middle clicking on the banner will still return the correct item.
Edit: Looks like this also affects colored beds, which always appear as white beds after being cloned.
This bug has been reported to our internal bug tracker for further testing and a fix. It is scheduled to be fixed in one of the future updates (no specific date can be provided).