Problem in scripting plugin. Need Help. Urgent

(scripting plugin)
I wrote the following piece of code in the console in gephi for changing all the colors of a graph( miserables.gexf)
for v in g.nodes:
... v.color=red

The error is :
Traceback (most recent call last):
File "", line 2, in
AttributeError: 'NoneType' object has no attribute 'color'

I also tried to print the source vertices of edges by the code
for e in g.edges:
print e.source
the error is:
Traceback (most recent call last):
File "", line 2, in
AttributeError: 'org.gephi.scripting.wrappers.GyEdge' object has no attribute 'source'
But, edges do have attributes 'source' and nodes have 'color' attribute as is said in wiki.gephi.org.

What seems to be the problem?? please help!!