Was just using it on my phone today when I finally realized what was missing, a dark mode/night theme for MaterialUI. Maybe located next to the color options under Settings > Menu.
@parkerlreed, if you know how to code, https://github.com/libretro/RetroArch/blob/master/menu/drivers/materialui.c is the source file you want to look at.
@Kivutar, the author of it, can probably do what you asked in less than an hour. I tried hacking at it and the maximum I could achieve was a gray chinbar. It's not immediately apparent to me what sets the foreground (text), background, active and inactive colors in that file.
I'll add that this feature would have the benefit of consuming significantly less power in devices with OLED displays.
Colors are here https://github.com/libretro/RetroArch/blob/master/menu/drivers/materialui.c#L719-L782
Here's what I got so far:

That's already nice!
@parkerlreed: Check out a nightly version of RetroArch. There should be a new menu option that will expose a couple of of new light colors and at least 1 darkish theme.
Remember to close the ticket.
Yeah, I'm fine with adding even more color themes later on.
:D love it http://i.imgur.com/VUUW4BT.png
Nice touch with the transparency under the bottom bar.
Most helpful comment
@parkerlreed: Check out a nightly version of RetroArch. There should be a new menu option that will expose a couple of of new light colors and at least 1 darkish theme.
Remember to close the ticket.