次のプログラムを改造して Node の色と大きさを変えました。
NetworkX と Matplotlib の使い方

example_sieze01.py

# ! /usr/bin/python
#
#	example_size01.py
#
#						Apr/18/2019
# ------------------------------------------------------------------
import sys
import networkx as nx
import matplotlib
import matplotlib.pyplot as plt
# ------------------------------------------------------------------
def draw_graph(edges):
	G = nx.DiGraph()
	G.add_edges_from(edges)
#
	# Specify the edges you want here
	edge_colours = ['black' for edge in G.edges()]
	black_edges = [edge for edge in G.edges()]

	# Need to create a layout when doing
	# separate calls to draw nodes and edges
	pos = nx.spring_layout(G)
	colors = ["red","green","yellow","blue","magenta"]
	sizes = [1200,1800,2400,3000,3600]
	nx.draw_networkx_nodes(G, pos, cmap=plt.get_cmap('Reds'), \
		node_color = colors, node_size=sizes)
	nx.draw_networkx_edges(G, pos, edgelist=black_edges, arrows=True)
	nx.draw_networkx_labels(G,pos,font_size=12,font_family='TakaoExMincho')
	
	plt.axis('off')
	plt.show()
#
# ------------------------------------------------------------------
edges = [('明治','大正'),('大正','昭和'),('昭和','平成'), \
		('平成','令和'),('令和','明治')]
draw_graph(edges)
# ------------------------------------------------------------------

実行結果