I just noticed something very strange. I created an Excel workbook in Excel 2010 (Windows 7) and manually formatted alternate rows with slightly different colors. When my colleague opened the document, all rows appeared as white.
I did some investigation and determined that the difference was tied to my Windows Appearance Settings. I like to keep my Window color setting at a light gray instead of white.
Here are some screenshots:
These screenshots were taken on my computer after my colleague recreated the alternating rows on his computer with standard Windows Appearance Settings.
Excel rows with Window color set to gray.

Excel rows with Window color set to white.

Has anyone seen this before? I could not find any linkage between Windows Appearance Settings and Excel Color Themes anywhere.