Apple iTunes 12 (on Mac OS) gives you no option for changing the background color. This can be a problem if, after an application update, you have a black background and black text, because you cannot easily use the iTunes interface.
To fix the background of your iTunes app on a Mac, enter and run the following command in your terminal window:
defaults write com.apple.iTunes high-contrast-mode-enable -bool FALSE
The command will restore your iTunes to its default settings and thereby restore the white background so that you can again use the application.