Yes, with matplotlib everything is possible.
The draw_networkx_nodes() function returns a collection object that
you can modify, e.g.
In [1]: import networkx as nx
In [2]: import pylab
In [3]: G=nx.path_graph(3)
In [4]: pos=nx.spring_layout(G)
In [5]: nodes = nx.draw_networkx_nodes(G,pos)
In [6]: nodes.set_edgecolor('r')
In [7]: pylab.draw()
You can set the colors, linestyle, zorder, etc, that way.
Aric