Replace color finding algorithm for writer

* Replace the algorithm that finds the most distinct colors for n used
  colors. This can currently color up to 255 nodes using hue spread.
  After that the program automatically adopts text coloring

src/SparseTransform/Convert/ColoredDotWriter.cs

 using SparseTransform.DataStructures;
+using System.Text;
 
 namespace SparseTransform.Convert
 {
@@ -9,7 +10,6 @@ namespace SparseTransform.Convert
     {
         private IGraph _coloredGraph;
         private bool _textcolor;
-        private string[] _dictColor = new string[65];
        
         /// <summary>
         /// Constructor constructing a color-dictionary for coloring purpose.
@@ -19,17 +19,6 @@ namespace SparseTransform.Convert
         {
             this._coloredGraph = graph;
             this._textcolor = textColor;
-
-            for (int i = 0; i <= 3; i++)
-            {
-                for (int j = 0; j <= 3; j++)
-                {
-                    for (int k = 0; k <= 4; k++)
-                    {
-                        _dictColor[i * 16 + j * 4 + k] = ("#" + (255 - i * 60).ToString("X2") + (255 - j * 60).ToString("X2") + (255 - k * 60).ToString("X2"));
-                    }
-                }
-            }
         }
        
         /// <summary>
@@ -40,14 +29,32 @@ namespace SparseTransform.Convert
         /// <returns></returns>
         public override String NodeLabel(GraphNode node, String prefix)
         {
-            if (_textcolor || node.Color > 64)
-            {
-                return "\t" + prefix + node.Index + "  [shape=circle, style=filled, label=\"" + prefix + node.Index + "\\n Farbe " + node.Color + "\"]";
-            }
-            else
+            // This is the offset. Less colors = more distance between
+            int hueFactor = 255 / _coloredGraph.ColorsUsed;
+            // Calculate the hue. We modulo with 255 to not exceed spectrum. Then convert to float for DOT
+            double hue = Math.Round((double)((node.Color * hueFactor) % 255) / 255, 3);
+
+            StringBuilder label = new StringBuilder();
+            // Append label name and general layout info
+            label.Append($"\t{prefix}{node.Index} [shape=circle, style=filled");
+
+            // If current node is colored, apply either text label with color or set fill color
+            if (node.Colored)
             {
-                return "\t" + prefix + node.Index + "  [shape=circle, style=filled, fillcolor=\"" + _dictColor[node.Color] + "\"]";
+                if (_textcolor || _coloredGraph.ColorsUsed > 255)
+                {
+                    label.Append($", label=\"{prefix}{node.Index}\\n color:{node.Color}\"");
+                }
+                else
+                {
+                    // Set saturation + value (brightness) to max for vibrant colors
+                    label.Append($", fillcolor=\"{hue} {1} {1}\"");
+                }
             }
+
+            // Close attribute line
+            label.Append("]");
+            return label.ToString();
         }
     }
 }