Excel 2003 Users
If you are wondering how you change the worksheet tabs color in an Excel spreadsheet then the title of this post might be a little deceiving. Unfortunately, this feature is not currently available in Microsoft Excel. It would certainly be helpful to many users to be able to color-code your worksheet tabs. For some unknown reason, Microsoft hasn't implemented this feature yet although I hear it has been available in 1-2-3 and Quattro Pro for quite a while. Still, that's not enough to make me quit using Excel and switching to another program.
Excel 2007 Users
You can easily change the tab color in Microsoft Excel 2007 by going to the home tab, clicking on the Cells section, going to Format and then hit "Change tab color." Easy.