Format trendline
You can change trendline properties in charts, such as line type, line color, or line weight.
If more than one measure is displayed you can specify the measure for which the trend line is to be shown.
Prerequisites
You are displaying a trendline in your chart.
Procedure. Procedure
Display the Base tab bar.
Click
Display options.Display the Chart settings/Labels page.
Click the Format trendline option.
Specify your settings.
Click OK.
The trendline is displayed with the new properties.