A lot of color in a spreadsheet can be distracting, but shades of gray are acceptable and naturally suited to visual expressing a gradient scale.
- Choose Options from the Tools menu and then click the Color tab.
- In the Chart Fills section, select any of the available color tiles. Don't choose one that you use frequently; choose a color that you seldom or never use.
- Click Modify.
- Click the Standard tab (the default) and choose a shade of gray that's not already on the palette.
- Click OK to return to the Color tab. Notice that the Chart Fills color you selected is now light gray.
- Repeat steps 2 through 5 to add enough shades of gray to accommodate your scale.