Maybe this will help.

http://support.microsoft.com/default.aspx?kbid=833258

The fill color, the fill pattern, or the line color of a WordArt or
AutoShape object in an Office document does not change

As directed, change the High Contrast setting in Windows OS


Gord Dibben MS Excel MVP

On Wed, 14 Feb 2007 09:52:08 -0800, Basher Bates
wrote:

Much of the cell formatting has just disappeared from my Excel 2003
worksheets since I recently installed Excel SP2. The colors are still
highlighted if I click on the fill or text button, so the formatting is still
there - just no displayed. If I now try to fill a cell nothing happens on
the screen. Merged cells, Borders, Outlines and Fonts are still displayed
correctly but look cramped because the column widths and row heights have
changed. I have checked several of my workbooks and they are all affected.
How can I correct the appearance of my work?