You can use the Reference Lines tab (Figure 9.18) to set attributes of reference lines that are displayed in the background of a plot.
The Reference Lines tab contains the following UI controls:
specifies the style of the line used for reference lines.
specifies the width of the line used for reference lines.
specifies the color of the line used for reference lines.
specifies whether to show reference lines for the X axis. These are vertical lines that originate at each tick mark on the X axis.
specifies whether to show reference lines for the Y axis. These are horizontal lines that originate at each tick mark on the Y axis.