Some very beautiful CD packaging was recently sent to me from the RX:TX label in Ljubijana, Slovenia. It’s a tri-panel CD pack with die-cut windows that show through various layers of card to reveal parts of the CD disc inside as the only colour.
The CD disc is designed so that it can be viewed either regular or upside down and the titles still readable. Depending on which way up you have the disc it changes the colours viewed through the windows on the other panels.