To format the style of the grid lines:
C1Chart3D1.ChartArea.AxisX.MajorGrid.Style.Color = Color.Blue
To turn off the grid lines, use the 3 methods IsOnXYPlane, IsOnYZPlane, and IsOnXZPlane, for each axis such as:
C1Chart3D1.ChartArea.AxisX.MajorGrid.IsOnXZPlane = False
hope that helps,
Greg L