Shading alternate rows in a large spreadsheet can improve legibility.  Excel’s Conditional Formatting feature allows you to apply cell shading to every other row in a worksheet range using the Modulus (=mod) function.

1. Select the range of cells or rows or columns to format.
   
   
2. Click Conditional Formatting from the Styles group on the Home tab of the Ribbon.  Select New Rule…
   
3. The New Formatting Rule dialog box displays. Select Use a formula to determine which cells to format.
   
4. Enter =MOD(ROW(),2)=0 in the Format values where this formula is true: field under Edit the Rule Description:
   
5. Click the Format… button.  The Format Cells dialog box displays.  Select the Fill tab to specify a color for the shaded rows. Click the OK button.
   • Note: Choose a light color to ensure enough contrast between text color and row shading.

6. The New Formatting Rule window displays with selected color in Preview: area. Click the OK button.
   
7. Alternating rows are formatted in the selected color.
   

    

   • Note: To update color
     1. Select the range of cells.
     2. Select Conditional Formatting from the Styles group on the Home tab of the Ribbon.  Select Manage Rules…
     3. The Conditional Formatting Rules Manager window displays with rules for the Current Selection listed.
        
     4. Select the Formula:=MOD(ROWS…0).  Click the Edit Rule… button.
     5. The Edit Formatting Rule window displays. Click the Format button
        .
     6. The Format Cells widows displays. Select a different color for row shading. Click OK
        .