Ahh... I have just noticed that you have Excel 2007 and this works for 2003. I am not sure if the same functionality is available in 2007.
In Excel, open a new workbook and save it as CustomColours.xls
Goto Tools - Options and select the Color tab.
Select each custom color in turn, modifying it to one of your custom colours.
Finally when all colours have been set as required click OK, and save the CustomColour.xls workbook.
At any time you have another workbook open and want the same set of custom colours, open CustomColours.xls at the same time.
Go back to the other Workbook, select Tools - Options and the Color Tab.
Below the colours is a box marked Copy colors from:
The drop down list will show CustomColours.xls.
Select it and your new workbook now has your set of custom colours.
Not the easiest procedure in the World, but it sure beats resetting all the colours individually.