It is possible to create custom colors with the color palette so that you can apply your company color scheme in your spreadsheet, thereby reinforcing your company brand.

I will use an example from the IBM Premiere Partner color scheme that defines IBM Blue as Pantone 2718 and Premiere Gold as Pantone 125.  The Excel color palette needs RGB values for custom colors and the IBM Guidelines for the Premiere Partner program provided those as R75  G107  B175 for IBM Blue and R192  G149  B10 for Premiere Gold.

From the menu bar select Tools, Option and then Color.  In the far right column (column 8) we're going to change the two shades of gray in rows 3 and 4 into IBM Blue and Premiere Gold respectively.  Select the color icon in column 8, row 4, click Modify and click the Custom tab.  For Red, Green and Blue enter 75, 107 and 175 respectively and then click OK, and OK again.  Our new IBM Blue color should now have replaced the gray icon.  Repeat the same steps with the icon in column 8, row 3, using 192, 149 and 10 respectively.

Now whenever you want to use the fill color icon (paintcan) to apply color to a cell, the IBM Blue and Premiere Gold will be a part of your color palette.  You can reset the color palette to the original colors at any time.

Your spreadsheet can implement your company Style Guide for font and color usage to match your other collateral materials.