Change DataGridView.GridColor when set. (#3869)

Actually change the GridColor when set. Add a test for GridColor.

Fixes #3829

Author: JeremyKuhne

src/System.Windows.Forms/src/System/Windows/Forms/DataGridView.cs

@@ -2775,6 +2775,7 @@ public Color GridColor
 
                 if (!value.Equals(GridPenColor))
                 {
+                    GridPenColor = value;
                     OnGridColorChanged(EventArgs.Empty);
                 }
             }

src/System.Windows.Forms/tests/UnitTests/System/Windows/Forms/DataGridViewTests.cs

@@ -6,6 +6,7 @@
 using System.ComponentModel;
 using Xunit;
 using WinForms.Common.Tests;
+using System.Drawing;
 
 namespace System.Windows.Forms.Tests
 {
@@ -2712,5 +2713,22 @@ private class SubDataGridView : DataGridView
 
             public new void OnRowHeadersWidthSizeModeChanged(DataGridViewAutoSizeModeEventArgs e) => base.OnRowHeadersWidthSizeModeChanged(e);
         }
+
+        [WinFormsFact]
+        public void DataGridView_GridColor()
+        {
+            using var dataGrid = new DataGridView();
+
+            int changedCount = 0;
+            dataGrid.GridColorChanged += (object sender, EventArgs e) =>
+            {
+                changedCount++;
+            };
+
+            dataGrid.GridColor = Color.Red;
+
+            Assert.Equal(1, changedCount);
+            Assert.Equal(Color.Red, dataGrid.GridColor);
+        }
     }
 }