In the recent snapshots, the satisfying graphic that appears in the loading screen when generating a new world has mysteriously changed colors from 1.17, now having a green border around the outside center square. I did not see this change mentioned on any of the official changelogs and I don't recall the graphic getting any color changes prior to this so it is likely that this is a bug.
The picture on the right is from the snapshot, left is from 1.17.