Marker styles are specified by the following properties:
marker
"none"
, meaning no markers should be displayed.
markeredgecolor
"auto"
, meaning that
the edge color is the same as the face color. See Colors.
markerfacecolor
"none"
to indicate that the marker
should not be filled. See Colors.
markersize
The colstyle
function will parse a plot
-style specification
and will return the color, line, and marker values that would result.