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
>I have always been able to view my highlighted cells while working in my
>document but recently, the only way to view highlighted cells is by
>previewing document or printing it out. Does anyone know how to correct this.
>
>Thank you