The border formatting surrounding the plot area. The fields within this group specify:
Setting the border option to None will disable the Style, Width, and Color fields.
Setting the border option to Custom will enable the Style, Width, and Color fields.
To modify the style, select the desired style from the drop-down list.
To modify the width, select the desired width from the drop-down list.
To modify the color, click on the colored button, select the desired color, and click OK.
NOTE: If the width is greater than 1 then the line style applied will always be solid.
Custom, Solid (for Style), 1point (for Width), and Black (for Color)
Plot Property page