I was trying to change my TeXworks editor's background to black, some suggested it is possible to edit this file :
but I could not locate this .txt file.
Thank you for your help!
In Windows, with MiKTeX 2.9 distribution, you can get the required file on the following path:
Username is your Windows user name.
Note also that this file is not for background colors but for text syntax highlighting. You can find more details in this link on how to customize colors and syntax highlighting.