LightGrayBG is a simple tweak to the IntelliJ Light theme, changing its editor background color from pure white to a more pleasant light gray (hex: #FAFAFA).
Unfortunately, IntelliJ-based IDEs do not allow their users to make such simple changes without enabling JetBrain's internal development tools — which is the reason for this simple theme's existence.
With the new UI introduced as a Beta in 2022.3, UI elements such as the tree view now have a light gray background per default. Thus, there is no need for a full plugin anymore, since customizing the remaining editor and and terminal views can be achieved via a simple theme file.
Get the LightGrayBG.icls theme file from the latest release and import it under Settings > Editor > Color Scheme > gear icon > Import Scheme
Get the LightGrayBG-1.x.zip plugin file from the v1.3 release and install it under Settings > Plugins > gear icon > Install Plugin from Disk