Merge pull request #4792 from michael-hawker/colorpickerslider-theme-change-fix

ColorPicker Slider Circle Accessibility Fix

Author: michael-hawker

Microsoft.Toolkit.Uwp.UI.Controls.Input/ColorPicker/ColorPickerSlider.cs

@@ -38,6 +38,8 @@ public ColorPickerSlider()
             : base()
         {
             this.DefaultStyleKey = typeof(ColorPickerSlider);
+
+            this.ActualThemeChanged += this.ColorPickerSlider_ActualThemeChanged;
         }
 
         /***************************************************************************************
@@ -297,5 +299,14 @@ private void OnDependencyPropertyChanged(object sender, DependencyPropertyChange
 
             return;
         }
+
+        /// <summary>
+        /// Event handler for when the control's theme changes.
+        /// </summary>
+        private void ColorPickerSlider_ActualThemeChanged(FrameworkElement sender, object args)
+        {
+            this.UpdateColors();
+            return;
+        }
     }
 }