[igraph] problem with painting edge.

[Domenico Conti]

Hi, I have a problem with igraph. I have a graph with following attributes:

graph.vs["name"] = ['Menelao', 'Adamante', 'Eurialo', 'Acasto', 
'Didone', 'Diomede', 'Aiace', 'Castore', 'Polluce']

graph.es["iFlow"] = [11, 57, 10, 60, 6, 40, 12, 90, 45, 51, 23, 35, 10, 
44, 67, 72, 27, 13, 45, 34, 16, 80]

I want plot a graph where each edge with an iFlow < 20 is painting with 
a grey color. But if its iFlow is > 20 is painting with a black color.