diff --git a/HISTORY.md b/HISTORY.md
index 71cc77d9..b4e3f4cd 100755
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -53,6 +53,7 @@
 
 ### 2021-11-10
 * objects, store: new "penColorModel" setting, can e 'hsv' or 'hsl'
+* gui, objects: new (hidden) pen-color-model preference setting (per session)
 
 ### 2021-11-09
 * objects, store: refactored block-migration mechanism
diff --git a/snap.html b/snap.html
index c99d778f..e40d76c1 100755
--- a/snap.html
+++ b/snap.html
@@ -20,7 +20,7 @@
         <script src="src/threads.js?version=2021-11-08"></script>
         <script src="src/objects.js?version=2021-11-10"></script>
         <script src="src/scenes.js?version=2021-10-12"></script>
-        <script src="src/gui.js?version=2021-11-09"></script>
+        <script src="src/gui.js?version=2021-11-10"></script>
         <script src="src/paint.js?version=2021-07-05"></script>
         <script src="src/lists.js?version=2021-07-19"></script>
         <script src="src/byob.js?version=2021-11-09"></script>
diff --git a/src/gui.js b/src/gui.js
index b35b599a..a27de4eb 100644
--- a/src/gui.js
+++ b/src/gui.js
@@ -86,7 +86,7 @@ BlockVisibilityDialogMorph*/
 
 // Global stuff ////////////////////////////////////////////////////////
 
-modules.gui = '2021-November-09';
+modules.gui = '2021-November-10';
 
 // Declarations
 
@@ -3845,6 +3845,22 @@ IDE_Morph.prototype.settingsMenu = function () {
             true
         );
     }
+    addPreference(
+        'HSV pen color model',
+        () => SpriteMorph.prototype.penColorModel = 'hsv',
+        SpriteMorph.prototype.penColorModel === 'hsv',
+        null,
+        null,
+        true
+    );
+    addPreference(
+        'HSL pen color model',
+        () => SpriteMorph.prototype.penColorModel = 'hsl',
+        SpriteMorph.prototype.penColorModel === 'hsl',
+        null,
+        null,
+        true
+    );
     addPreference(
         'Input sliders',
         'toggleInputSliders',
diff --git a/src/objects.js b/src/objects.js
index ededa66b..37c3b2c7 100644
--- a/src/objects.js
+++ b/src/objects.js
@@ -4449,7 +4449,10 @@ SpriteMorph.prototype.setColorDimension = function (idx, num) {
         this.color.a = 1 - n / 100;
     } else {
         this.cachedColorDimensions[idx] = n / 100;
-        this.color.set_hsl.apply(this.color, this.cachedColorDimensions);
+        this.color['set_' + this.penColorModel].apply(
+            this.color,
+            this.cachedColorDimensions
+        );
     }
     if (!this.costume) {
         this.rerender();
@@ -9295,7 +9298,10 @@ StageMorph.prototype.setColorDimension = function (idx, num) {
         this.color.a = 1 - n / 100;
     } else {
         this.cachedColorDimensions[idx] = n / 100;
-        this.color.set_hsl.apply(this.color, this.cachedColorDimensions);
+        this.color['set_' + SpriteMorph.prototype.penColorModel].apply(
+            this.color,
+            this.cachedColorDimensions
+        );
     }
     this.rerender();
 };