To add or modify a border, complete the following steps:

1.   In the Properties window, expand the ChartArea node.

2.   Expand Style node.

3.   Expand Border node.

4.   Select style type from the BorderStyle drop-down menu.

5.   Select desired color from the Color drop-down menu.

6.   Increase number of Thickness property to make border more prominent or decrease number to make border less prominent.

For more information, see Chart Borders.