Isn't Nintendo the blue one, though?

PS4 cases are already a bit slimmer.  Not sure how much smaller they can get.  Still better than these:

Are you for real?

Dimensions of Vita case:

Dimension: 4" x 5 1/4" x 10mm.  

faA BD has a diameter of ~4.8 inches. Hence it would very nearly fit in a Vita case. And I said "like" the Vita cases, implying something similar. Those big DVD boxes the games come in look archaic.

Blue of Hope to counter the Will of Green.

I loved this change to blue box! It is beautiful and modern.

Nice reference sales!

How come some PS4 box art is purple-blue, and other is darkblue-lightblue?

Not familiar as look same to me on PS4. Can you provide some examples?

Yeah. That way PS3, PSV, and PS4 all match.

I think so. IN Square-enix' store, some of their soon to be released ps3 games have also changed in color, like Drakengard 3 for example.