A color scheme that matches the grey and teal color scheme of Android, allowing for more consistency across usage!
One of the ticks about the app is that there isn't a single color scheme that fits the rest of Android. I understand that it may be an attempt to differentiate itself from other apps, but an increased fluency between apps would overall be much nicer.
I get that some people would rather have a bunch of colors for each app, but at some point it gets tiring. A consistent color scheme would make the app a little more "professional".
The color scheme I'm talking about is the one in the settings app in Android 6.0—or the Google keyboard.