http://www.graphviz.org/doc/info/colors.html

线颜色

	subgraph cluster_api {
		#rank=same;
		node [style=filled];
		label = "api";
		#color=blue
		api [label = "api.netkiller.cn"];
		api->redis [color="red"];
		api->mongodb [color="green"];
		api->oracle [color="blue"];
		
	}
			

http://www.graphviz.org/doc/info/shapes.html

digraph G {  
	A -> B [arrowhead="vee"]
	AA -> BB [dir="back" arrowtail="vee"]
	AAA -> BBB [dir="both" arrowhead="vee" arrowtail="odiamond"]
}