Color palette in Excel-embedded data in PPT

Excel 2003 and PowerPoint 2003; Windows XP Pro

I'm a PowerPoint specialist working within PPT on graphs with embedded Excel data -- so not working directly in Excel, and don't have access to the original Excel spreadsheets. Within that context, I would like to change the available color palette (i.e., update by RGB numbers) for these graphs to match our corporate palette. I appears these are fixed but I'm sure someone knows a work-around. Any help is appreciated!

SEN

Hmmm. . . we may be talking about different things.

If I "open" the graph by double-clicking -- thereby enabling access to the data -- and right click on an element (say, I bar in a bar graph), one of my choices is "Format Data Series" or "Format Data Point". ("Chart Type" and "Source Data" don't seem to contain anything germaine to this issue.) In the window that opens, my choices are "Patterns", "Data Labels" and "Options"; again, only "Patterns" appears to be germaine. From there, the color palette available seems fixed, meaning I can choose from 56 colors (several appearing to be duplicates. . .) but don't see any option to actually change the RGB values -- something I can do in a standard (non-Excel-embedded) PPT entity. So that's what I'm trying to do: change the RGB values in the embedded graph.