The Windows "Window" color isn't honored for the spreadsheet background
Submitted by Dan Dascalescu
In Windows, you can go to Control Panel -> Display -> Appearance -> Advanced, pick the "Window" item, and change its color. This reflects in the background color of applications that honor this setting: MS Word, MS Excel, IE etc.
The default color is a bright white, and I've found that when working many hours on a document, this would hurt my eyes. Setting the color to gray makes it much more tolerable. To test, simply open a new Word or Excel document.
Gnumeric unfortunately doesn't honor this accessibility setting so I'll have to stay with Excel for now.