I have two that have different colored backs for Xena Seasons 4 and 5 P4, but I'm not certain if its something to do with the ink or if it is intentional.

The back of P2 from that set (its the only two numbers I have right now) has a purple colored section on either side of the text, and the color behind the text is a blue hue. That same color design is on the back of one of the P4s I have.

The other P4 has the same purple on either side of the text, but the color behind the text is purple, not blue.

Can some of you check your P4 and see what you see?