Graphics Query, Edit, and Defaults

plq                  query (print) legends for current window 
plq, i               query properties of element i
pledit, key_list     change properties of queried element 
pldefault, key_list  set default window and element properties

The keywords which regulate the appearance of graphical primitives include (each has a help entry):

legend     string to use for legend
hide       non-zero to skip element
type       "solid", "dash", "dot", "dashdot", etc.
width      line width, default 1.0
color      "fg" (default), "red", "green", "blue", etc.
marks, marker, mspace, mphase, msize  line markers
rays, rspace, rphase, arroww, arrowl  line ray arrows
closed, smooth   more line properties
font, height, opaque, path, justify   text properties
hollow, aspect   vector properties for plv