The background color can be changed by starting Performance Manager with a different background color; for example:

   pmgr -fg black -bg salmon

You might want to do this to provide greater viewing contrast, but be careful not to choose a color that will obscure text, such as a black foreground that hides black text.

You can also modify the font and the foreground and background colors used in the interface by editing the X resource file /usr/lib/X11/app-defaults/PM.