See my picture and there is a cell A3 which has no top border. when i set top border but still getting no border. so curious to know how to set top border with default color.

ws.Cells["A3"].Style.Border.Top.Style = ExcelBorderStyle.Thin;
ws.Cells["A3"].Style.Border.Bottom.Color.SetColor(System.Drawing.Color.Transparent);
here i set Color.Transparent. i like to know what i need to set default border colour ?
I have to set default border colour for top border for A3 cell. please suggest me something.
Thanks