Excel needs to know when you have completed a sheet. Say we pick B9. If you
enter a value in B9 Excel will do the coloring. Enter this event macro in
the worksheet code area:
Private Sub Worksheet_Change(ByVal Target As Range)
If Intersect(Target, Range("B9")) Is Nothing Then Exit Sub
ActiveSheet.Tab.ColorIndex = 10
End Sub
Because it is worksheet code, it is very easy to install and automatic to use:
1. right-click the tab name near the bottom of the Excel window
2. select View Code - this brings up a VBE window
3. paste the stuff in and close the VBE window
If you have any concerns, first try it on a trial worksheet.
If you save the workbook, the macro will be saved with it.
To remove the macro:
1. bring up the VBE windows as above
2. clear the code out
3. close the VBE window
To learn more about macros in general, see:
http://www.mvps.org/dmcritchie/excel/getstarted.htm
To learn more about Event Macros (worksheet code), see:
http://www.mvps.org/dmcritchie/excel/event.htm
Repeat for each worksheet.