This mod replaces the default bright note background with a more eye-friendly background. Please read the readme file included in the mod.
Copypaste of the readme file:
Go to the Penumbra directory (Right click on the left side of your Steam library, manage, browse game files)
Navigate to the filepath here
Copy the files from this directory to that place, replace any existing files.
Just delete the dark notebook files (3 of them in total) and delete the "_backup" from the light theme files, then restart the game.
Confused, want help?
Not sure what there is to help with, but...
There should be a person called June (or something) there, DM/ping her. If you can't find her, try to ask in the Penumbra chat.