Why did Android switch basic menu styles to white background from the old black one?

[AC Question]

Prior to the most recent Android update, most of the menu style backgrounds were a dark gray or black. Now ever since the last update all of the menu styles are white (like in messages or the settings menu). There's a reason I chose Android over iPhone, because having everything white (like for iPhone) is annoying and I liked that Android has more customization options (or so I thought).
I preferred the black background because a) it saves on battery life, b) it's easier on the eyes late at night, and c) it's just a personal aesthetic preference.
I'm hoping that with the next Android update you can customize themes that affect the background colour of the menus et al.

 

[B. Diddy]

Welcome to Android Central! It was part of Material Design, an effort to unify the Android look. https://www.google.com/design/spec/material-design/introduction.html#introduction-principles