The interface theme defines the appearance of windows, dialogs, and controls.
Change the UI theme
In the Settings/Preferences dialog Ctrl+Alt+S, select Appearance & Behavior | Appearance.
Select the UI theme from the Theme list:
Darcula: Default dark theme
Light: More traditional light theme
High contrast: Theme designed for users with color vision deficiency
It is also possible to create your own UI themes for MPS and customize the built-in themes. For more information, see IntelliJ Platform SDK Documentation.