Added a menu item to reset the pen color (to use again the plotColorPalette based color). Moved the saving/loading code to the SensorNode class (as with the other properties).

GUI/HardwareNode.cs

@@ -89,8 +89,6 @@ namespace OpenHardwareMonitor.GUI {
         ((SensorNode)node.Nodes[i]).Sensor.Index < sensor.Index)
         i++;
       SensorNode sensorNode = new SensorNode(sensor, settings, unitManager);
-      if (settings.Contains(sensor.Identifier + "/PenColor"))
-        sensorNode.penColor = settings.GetValue(sensor.Identifier + "/PenColor", Color.Black);
       sensorNode.PlotSelectionChanged += SensorPlotSelectionChanged;
       node.Nodes.Insert(i, sensorNode);
     }

GUI/MainForm.Designer.cs

@@ -111,7 +111,6 @@ namespace OpenHardwareMonitor.GUI {
       this.log1hMenuItem = new System.Windows.Forms.MenuItem();
       this.log2hMenuItem = new System.Windows.Forms.MenuItem();
       this.log6hMenuItem = new System.Windows.Forms.MenuItem();
-      this.colorDialog = new System.Windows.Forms.ColorDialog();
       this.splitContainer.Panel1.SuspendLayout();
       this.splitContainer.SuspendLayout();
       this.SuspendLayout();
@@ -763,7 +762,6 @@ namespace OpenHardwareMonitor.GUI {
     private System.Windows.Forms.MenuItem log1hMenuItem;
     private System.Windows.Forms.MenuItem log2hMenuItem;
     private System.Windows.Forms.MenuItem log6hMenuItem;
-    private System.Windows.Forms.ColorDialog colorDialog;
   }
 }
 

GUI/MainForm.cs

@@ -494,7 +494,7 @@ namespace OpenHardwareMonitor.GUI {
         SensorNode sensorNode = node.Tag as SensorNode;
         if (sensorNode != null) {
           if (sensorNode.Plot) {
-            if (sensorNode.penColor == null) {
+            if (!sensorNode.PenColor.HasValue) {
               colors.Add(sensorNode.Sensor,
                 plotColorPalette[colorIndex % plotColorPalette.Length]);
             }
@@ -528,8 +528,8 @@ namespace OpenHardwareMonitor.GUI {
 
       foreach (TreeNodeAdv node in treeView.AllNodes) {
         SensorNode sensorNode = node.Tag as SensorNode;
-        if (sensorNode != null && sensorNode.Plot && sensorNode.penColor != null)
+        if (sensorNode != null && sensorNode.Plot && sensorNode.PenColor.HasValue)
-          colors.Add(sensorNode.Sensor, sensorNode.penColor.Value);
+          colors.Add(sensorNode.Sensor, sensorNode.PenColor.Value);
       }
 
       sensorPlotColors = colors;
@@ -683,17 +683,23 @@ namespace OpenHardwareMonitor.GUI {
           }
           treeContextMenu.MenuItems.Add(new MenuItem("-"));
           {
-            MenuItem item = new MenuItem("Pen color");
+            MenuItem item = new MenuItem("Pen Color...");
             item.Click += delegate(object obj, EventArgs args) {
-              colorDialog.Color = node.penColor.GetValueOrDefault();
+              ColorDialog dialog = new ColorDialog();
-              if (colorDialog.ShowDialog() == DialogResult.OK) {
+              dialog.Color = node.PenColor.GetValueOrDefault();
-                node.penColor = colorDialog.Color;
+              if (dialog.ShowDialog() == DialogResult.OK)
-                settings.SetValue(node.Sensor.Identifier + "/PenColor", colorDialog.Color);
+                node.PenColor = dialog.Color;
-                PlotSelectionChanged(this, null);
-              }
             };
             treeContextMenu.MenuItems.Add(item);
           }
+          {
+            MenuItem item = new MenuItem("Reset Pen Color");
+            item.Click += delegate(object obj, EventArgs args) {
+              node.PenColor = null;
+            };
+            treeContextMenu.MenuItems.Add(item);
+          }
+          treeContextMenu.MenuItems.Add(new MenuItem("-"));
           {
             MenuItem item = new MenuItem("Show in Tray");
             item.Checked = systemTray.Contains(node.Sensor);

GUI/MainForm.resx

@@ -129,9 +129,6 @@
   <metadata name="timer.TrayLocation" type="System.Drawing.Point, System.Drawing, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a">
     <value>293, 17</value>
   </metadata>
-  <metadata name="colorDialog.TrayLocation" type="System.Drawing.Point, System.Drawing, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a">
-    <value>483, 17</value>
-  </metadata>
   <assembly alias="System.Drawing" name="System.Drawing, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" />
   <data name="$this.Icon" type="System.Drawing.Icon, System.Drawing" mimetype="application/x-microsoft.net.object.bytearray.base64">
     <value>

GUI/SensorNode.cs

@@ -4,7 +4,7 @@
   License, v. 2.0. If a copy of the MPL was not distributed with this
   file, You can obtain one at http://mozilla.org/MPL/2.0/.
  
-  Copyright (C) 2009-2012 Michael Möller <mmoeller@openhardwaremonitor.org>
+  Copyright (C) 2009-2016 Michael Möller <mmoeller@openhardwaremonitor.org>
 	
 */
 
@@ -22,7 +22,7 @@ namespace OpenHardwareMonitor.GUI {
     private UnitManager unitManager;
     private string format;
     private bool plot = false;
-    public Color? penColor = null;
+    private Color? penColor = null;
 
     public string ValueToString(float? value) {
       if (value.HasValue) {
@@ -61,6 +61,10 @@ namespace OpenHardwareMonitor.GUI {
 
       this.Plot = settings.GetValue(new Identifier(sensor.Identifier, 
         "plot").ToString(), false);
+
+      string id = new Identifier(sensor.Identifier, "penColor").ToString();
+      if (settings.Contains(id))
+        this.PenColor = settings.GetValue(id, Color.Black);
     }
 
     public override string Text {
@@ -77,6 +81,22 @@ namespace OpenHardwareMonitor.GUI {
       }
     }
 
+    public Color? PenColor {
+      get { return penColor; }
+      set {
+        penColor = value;
+
+        string id = new Identifier(sensor.Identifier, "penColor").ToString();
+        if (value.HasValue)
+          settings.SetValue(id, value.Value);
+        else
+          settings.Remove(id);
+
+        if (PlotSelectionChanged != null)
+          PlotSelectionChanged(this, null);
+      }
+    }
+
     public bool Plot {
       get { return plot; }
       set { 

OpenHardwareMonitor.csproj

@@ -66,7 +66,6 @@
     </Reference>
     <Reference Include="System" />
     <Reference Include="System.Configuration.Install" />
-    <Reference Include="System.Data" />
     <Reference Include="System.Drawing" />
     <Reference Include="System.Management" />
     <Reference Include="System.Windows.Forms" />