Excel, by default comes with a standard pre-selected color palette, which is useful, however there are times when those standard colors just won’t do.
It’s possible that your company’s colors are not included in the standard colors found in Excel. If you’d like to use them in your workbook, you’ll need to change the standard colors.
In order to do this, select Tools | Options | Colors tab (in pre-2007 versions of Excel), or Microsoft Office Button | Excel Options | Save | Colors (in Excel 2007).
Next, click on the color you wish to change, and click Modify. You can choose from one of the colors on the Standard tab, or you can click the Custom tab if you know the RGB or HSL format of the color you wish to use.
Repeat these steps as often as necessary, then when you return to Excel, you can change the fill, font, and chart colors in your workbook to your new custom colors.