You can display gridlines behind a bar, line, or combo chart. You can show or hide gridlines, and you can specify gridline color, style, and background color.
To define gridlines:
On the Chart Properties property sheet, click the Format Chart button.
From the Gridlines drop-down list, select one of the following options:
Optional: To specify a style (solid, dotted, dashed, dotdash, or bar) for the gridlines, click Gridline Style and select an option from the drop-down list.
Optional: To specify a color for the gridlines, click Gridline Color and select a color from the drop-down color palette.
Optional: To specify a background color to display behind the gridlines, click Grid Background and select a color from the drop-down color palette.