Android M vs Android 5.1 Lollipop Walkthrough: What’s New So Far

Android 5.1 vs Android M - Settings Menu

As you can see in this slide the settings menu is almost 100% the same. However, Google's finally added themes to the settings menu. Allowing users to have a white theme for settings, or a dark mode. This is hidden in developer options for now, but may be an easy option in settings once Android M is released.