Making the white bar below the keyboard black I just got a new OnePlus 5T. I like to use a dark theme whenever possible, including the Android keyboard. In many apps, the bottom bar is white. (I'm talking about the navigation bar which has the three buttons, back, minimize and show active apps.)

Here are a couple of examples:




Any idea how I could make it black?
Use substratum theme engine for this purpose. You can theme individual ui element with the help of this. You screenshot looks like you are using oreo build so you can use substratum even without root. Check out this link 
https://www.xda-developers.com/custom-themes-android-oreo-substratum/