Select reference line > Editor > Edit Reference Line > Attributes
Specify the type, color, and size of reference lines. To add a reference line to a graph, choose Editor > Add > Reference Lines.
Lines
Automatic: Choose to accept the default line attributes.
Custom: Choose to change the line attributes.
Type: Choose a line type.
Color: Choose a line color.
Size: Choose a line thickness.
Apply same attributes to all reference lines: Check to apply attribute changes to all reference lines in the graph.