Here you'll learn to change the theme of Android Studio IDE.
This is not the procedure to change the theme of the app but the Android Studio IDE itself.

Changing Android Studio IDE Themes | Kodewaala

Firstly for Windows Versions of Android Studio IDE

In the scheme, name select Darcula and apply to see a awesome dark background theme editor.

File->Settings->Editor->Colors & Fonts-> 

For Android Studio 3.1.2

In the scheme, name select Darcula and apply to see a awesome dark background theme editor

File->Settings->Editor->Color Scheme-> 


Applying theme from the jar file

You can download new themes from http://color-themes.com/

Once you have the jar file downloaded from the above source. Go to File -> Import Settings...  And choose the downloaded file to apply the theme.



On Mac OS changing Android Studio IDE Theme

Get the theme in .icls file and put them at 

~/Library/Preferences/AndroidStudio/colors
After you placed them at the above path, restart the Android Studio IDE.

Now, 
Select the imported theme at

Android Studio > Preferences > Editor > Colors&Fonts

Android Studio can use any theme that is made for JetBrains IDE. Here is a good Github repo that has many themes for different IDEs.

Also, the Color Ide plugin is a good tool that changes the background colour of all menus in Android Studio to match your theme.