How to change the Spyder editor background to dark?

For Spyder 2.3 which is still installed via apt-get on linux, you change the theme via

Tools > Preferences > Editor > Syntax Color 

The

Tools > Preferences > Syntax Coloring

only shows options for adjusting the different themes, but not actually applying a different theme. Spyder 3.x uses the second option via Syntax Color.

Tools->Preferences->Syntax coloring->Scheme changed to "Spyder Dark"

If you're using Spyder 3, please go to

Tools > Preferences > Syntax Coloring

and select there the dark theme you want to use.

In Spyder 4, a dark theme is used by default. But if you want to select a different theme you can go to

Tools > Preferences > Appearance > Syntax highlighting theme