I changed my color scheme from Default to Dracula, and along with the syntax colouring, the Android Studio interface was set to dark as well.
However, now if I select the Default theme again, the interface remains dark, and would not change back to light grey/white as it should.
I read that in other version's of Android Studio you could change the interface color from Preferences > Editor > General > Appearance, but I cannot find any theme-related settings there.
I found the theme (interface) option, in OSX is actually under Preferences > Appearance & Behaviour > Appearance.
It is not that straightforward considering the syntax colouring options are in another section entirely :/