graph display(please help)

[questions?]

I heard from my friend who used to program in JAVA, it is really easy
to do graph display in JAVA.

I wonder whether there are similiar packages in Python I can use. Since
I know a little bit Python syntax  already, I can easily learn more in
Python.

I want to display connected graph(directed or undirected, most often
trees) with coloring on them.

Thanks for any suggestions!!!