I use the Dark (Black) setting, to reduce the eye strain.
Have AutoCAD set with Black Backgrounds - for Model and Layout(s).
MS Word is set with Blue Background.
Would be great to set Excel with darker views of Spreadsheets, especially since I perform >40% of a project's Engineering / Design tasks via Excel.
Back in the day (1990 - 1995), most of the Apps were DOS Apps, so the "Background" was Black (or a charcoal Gray).
My 80386 Machine had an EGA Monitor, which included a Manual switch to go into Monochrome (Green Scale), or back to Color mode - with the EGA's whopping 16 Colors!
Was great for MS Word / Excel for Windows (view in Monochrome).
Also was nice for Word Star (DOS), and the "Has To Be The Origin Of HTML" tagging used to format a Document!
(if you remember Word Star, you know what I am talking about!)
Scott