[BioC] How to distinguish two overlapped nodes

[Jiayi Hou [guest]]

I wonder does anybody know how to draw to distinguish two color-filled overlapped nodes in Rgraphviz. For example, I want to draw two nodes, a smaller one filled with green and a bigger one filled with red. I dont want the green one hidding behind the red one for it can only be seen partially or completely invisible. Is there anyway to ensure the green node always comes in front of the red node so it can be seen completely? 

Thanks 

 -- output of sessionInfo(): 

R version 2.12.2 (2011-02-25)
Platform: i386-pc-mingw32/i386 (32-bit)

locale:
[1] LC_COLLATE=English_United States.1252  LC_CTYPE=English_United States.1252   
[3] LC_MONETARY=English_United States.1252 LC_NUMERIC=C                          
[5] LC_TIME=English_United States.1252    

attached base packages:
[1] grid      stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
Rgraphviz_1.28.0     graph_1.28.0        


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