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.