add in the docstring of pydotprint info about the new color used.

theano/printing.py

@@ -391,6 +391,8 @@ def pydotprint(fct, outfile=os.path.join(config.compiledir,'theano.pydotprint.pn
     green ellipse are input to the graph
     blue ellipse are output of the graph
     grey ellipse are var generated by the graph that are not output and are not used.
+    reb ellipse are transfer to/from the gpu.
+        op with those name GpuFromHost, HostFromGpu
     """
     if not isinstance(mode,ProfileMode) or not mode.fct_call.has_key(fct):
         mode=None