You probably have protected the worksheet, another possibility is
sharing. I have a page on grayed out things.
http://www.mvps.org/dmcritchie/excel/grayedout.htm

Unprotect the worksheet, change your conditional formatting and
turn protection back on -- it that was the problem.
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HTH,
David McRitchie, Microsoft MVP - Excel [site changed Nov. 2001]
My Excel Pages: http://www.mvps.org/dmcritchie/excel/excel.htm
Search Page: http://www.mvps.org/dmcritchie/excel/search.htm

"dgams" wrote...
I am working on a spreadsheet in excel 2003. I have a column of dates and I
want to format each month to have a different color. Under format,
conditional formatting is in gray and won't allow me to select it. Does
anyone know what I'm doing wrong?