When I use color fill to color the background of a cell, it does not show on the worksheet on the monitor, but it does print out shaded.

Suggestion #1:
Make sure the High Contrast setting is not enabled on the Display tab of the Accessibility Options in the Control Panel.
The fill color, the fill pattern, or the line color of a WordArt or AutoShape object in an Office document does not change (http://support.microsoft.com/kb/833258/en-us)

Suggestion #2:
Try Tools > Options > Colors and touch Reset

Thanks buddy. It worked immediately

Dammit! You are a genius!
Thanks a lot. Ended my struggle instantly