fillcolor is not defined,
used. (For clusters, if
color is not defined,
bgcolor is used.) If this is not defined,
the default is used, except for
shape=point or when the output
which use black by default.
If the value is a
colorList, a gradient fill is
used. By default, this is a linear fill; setting
cause a radial fill. At present, only two colors are used. If the second
color (after a colon) is missing, the default color is used for it.
See also the
for setting the gradient angle.