Foreground color is used to draw the boundary shapes of edited objects.

 Foreground colors can be changed individually, or on selected sets of
 objects altogether, through any color button in the <Attribute>:<Foreground>
 menu. Colors can be reverted to original (<Attribute>:<Foreground>:<Default>).
 Color buttons in the menu are assigned through X11 resources

atg*foreground<int>  (for instance atg*foreground5 : green ), and

 their number must be provided as: 

atg*nbForegrounds : <int>

 The default foreground value for each object type is set by resources, as
 well as a foreground for highlighting them. Resources names are:

atg*boxForeground
atg*hilightBoxForeground

 and similarly for vertex, port, edge, web instead of box.