Each pane on the Process Analyst can have one selected pen. The axes that are displayed on a pane are that of the selected pen. The last pen selected across every pane is referred to as the primary selected pen.
You can select a Process Analyst pen in several ways:
The selection of a pen is indicated by a subtle halo effect surrounding the pen line. In the example shown here, the top (green) pen is selected, indicated by the halo surrounding the pen:
The halo does not appear if there is only one pen on the pane. Selecting a pen on a pane also causes the same pen to be highlighted in the Object View. Selecting a pen causes that pen to be drawn in front of other pens on the pane.