When a script or EA is highlighting calendar events with vertical lines, this specifies the line width to use. I tend to highlight high risk calendar events as red, medium risk as orange and low risk as yellow.
When a script or EA is highlighting bank holidays with vertical lines, this specifies the line width to use. I tend to use dotted lines instead of solid lines if the line width is 1.
During the time when new trades are not allowed and those time periods are being shown on a chart by vertical lines, this input specifies the colour of the vertical lines used.