property InsideZoomFormat.GridLineColor as Color
Specifies the grid line color for the inside level.

TypeDescription
Color A Color expression that defines the unit's grid lines color. 
Use the DrawGridLines property to show or hide the unit's grid lines. The grid lines are shown in the chart area only, if the DrawGridLines property is True and the DrawGridLines property of the Chart object is not exNoLines or exHLines. The GridLineStyle property specifies the style to shown the vertical gridlines inside the time-scale unit. The BackColorChart property specifies the unit's background color being shown in the chart ( not in the header ).

The following screen shot shows the grid lines in red: