Brian

I have not heard of being able to purchase software to add more colors to
Excel's palette.

Excel will allow 56 colors at a time.

You can modify these by going to Tools>Options>Color>Modify.

You can also import colors from a workbook that already has the colors
modified.

See same Color Tab for "Copy colors from".  The other workbook must be open.

For more on Excel Colors see David McRitchie's site.

http://www.mvps.org/dmcritchie/excel/colors.htm

Gord Dibben Excel MVP