Answer:
In RFEM 5 and RSTAB 8, you can change the background color in "Display Properties". To do this, go to the menu and select Options → Display Properties → Edit. In Colors → Other category, you can then define a different color for the background. Optionally, you can also set the background gradient in the General → Graphical Effects category.
The default profile with a white background can be set quickly in the Configuration Manager that is available in the Options → Configuration Manager menu in RFEM 5 and RSTAB 8. Select the "Standard with white background" option there and set this configuration as current by clicking the button with the blue check mark.
