Cluster Gradients

digraph G {bgcolor="#0000FF44:#FF000044" gradientangle=90
	fontname="Helvetica,Arial,sans-serif"
	node [fontname="Helvetica,Arial,sans-serif"]
	edge [fontname="Helvetica,Arial,sans-serif"]

	subgraph cluster_0 {
		style=filled;
		color=lightgrey;
		fillcolor="darkgray:gold";
		gradientangle=0
		node [fillcolor="yellow:green" style=filled gradientangle=270] a0;
		node [fillcolor="lightgreen:red"] a1;
		node [fillcolor="lightskyblue:darkcyan"] a2;
		node [fillcolor="cyan:lightslateblue"] a3;

		a0 -> a1 -> a2 -> a3;
		label = "process #1";
	}

	subgraph cluster_1 {
		node [fillcolor="yellow:magenta" 
			 style=filled gradientangle=270] b0;
		node [fillcolor="violet:darkcyan"] b1;
		node [fillcolor="peachpuff:red"] b2;
		node [fillcolor="mediumpurple:purple"] b3;

		b0 -> b1 -> b2 -> b3;
		label = "process #2";
		color=blue
		fillcolor="darkgray:gold";
		gradientangle=0
		style=filled;
	}
	start -> a0;
	start -> b0;
	a1 -> b3;
	b2 -> a3;
	a3 -> a0;
	a3 -> end;
	b3 -> end;

	start [shape=Mdiamond ,
		fillcolor="pink:red",
		gradientangle=90,
		style=radial];
	end [shape=Msquare,
		fillcolor="lightyellow:orange",
		style=radial,
		gradientangle=90];
}