Update 1: 2018/08/18 8:56am PDT
For whatever reason, Google has seemingly decided to pull the update (which was server-based) for everyone. We're not sure why as there didn't seem to be any major issues with
Both Google Phone and Google Contacts had Material redesigns earlier this month. As such, people began speculating that Android Messages would also soon be revamped, and now it's happened. On top of the redesign, version 3.5 of Android Messages also brings a long-awaited dark mode.Read More
[Update: Reverting] Android Messages v3.5 adds new Material UI with dark mode [APK Download] was written by the awesome team at Android Police.