Weird background color on the project files

Please check Settings (Preferences on macOS) | Appearance & Behavior | File Colors. Did you customize any scopes/colors there?

Does the issue occur for all projects?

Thanks for replying.
This is happening for only this particular project. I tried deleting the idea directory. But this color reappears after setting the poetry venv in the preferences. 

I just reselected the python venv and that color is gone now. It is weird, anyway this is solved. Thanks.