public static void uncolorVertex(UndirectedGraph<Vertex> g, Vertex v) {
		int oldColor = v.getColor();
		if(oldColor >= 0) {
			v.setColor(-1);
			for(Vertex u : g.getNeighbors(v)) {
				// See if u still has neighbor with oldColor
				boolean stillPossible = true;
				for(Vertex w : g.getNeighbors(u)) {
					if(w.getColor() == oldColor) { stillPossible = false; break; }
				}
				// Otherwise mark u as colorable with oldColor
				if(stillPossible) u.setPossible(oldColor, true);
			}
		}
	}