The first thing to do would be to check you display settings:
1. Click on Start > Control Panel > Accessibility options> Display tab
2. Uncheck the box ‘Use High Contrast’.
3. Click on Apply then OK.

Another possibility is that the affected application is running in compatibility mode. To check/remedy this:
1. Browse to the following location: C:\Program Files\Microsoft Office\Office 12.
2. Locate the file excel.exe (since your posted image suggests you're having trouble with that).
3. Right click on the file and then click on the properties option.
4. Click on the compatibility tab.
5. Uncheck ‘Run this program in compatibility mode for’ checkbox and click Ok.
6. Now open the Excel and check the Ribbon color.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]