if (graph.Directed == true) throw new ArgumentException();

            colors = new int[graph.VerticesCount];
            int maxColor = 0;
            colors[0] = maxColor; //najwyzszy kolor
            for (int i = 1; i < graph.VerticesCount; i++)
            {
                colors[i] = int.MaxValue;
            }
            for (int v = 0; v < graph.VerticesCount; v++)
            {
                if (graph.InDegree(v) == 0)
                {
                    colors[v] = 0;
                    continue;
                }

                for (int k=0;k<=maxColor;k++)
                {
                    bool isColorUsed = false;
                    foreach(Edge e in graph.OutEdges(v))
                    {
                        if (colors[e.To] == k)
                        {
                            isColorUsed = true;
                            break;
                        }
                    }
                    if (!isColorUsed)
                    {
                        colors[v] = k;
                        break;
                    }
                }
                if (colors[v]==int.MaxValue)
                {
                    maxColor++;
                    colors[v] = maxColor;
                }
            }
            return maxColor + 1;