Mega Background has been altered to its previous version in the new update.

Unofficial identification for each background:

– ​Rainbow Mega Symbol with Red flare backdrop

(Original Day 1)

– Rainbow Mega Symbol with black backdrop

(2.0 version, aka current version)

– Red Mega Symbol with black backdrop

(3.0 Change, aka previous version)

Edit: Title is confusing to anyone who does not know about the order of change​, but to sum up the order of change…

Original Day 1 -> 2.0 -> 3.0 -> 2.0

When I say "previous" in the title, it's talking about the 2.0 version. In the images, 3.0 is now the previous as the current is 2.0.