How to change the border color (or remove the border) of a PropertyGrid control?

this is another alternative, as it seems that my first answer is not suitable for this particular control. This is a dirty trick but should work:

Put a Panel control in your window or dialog, let say with size 100H x 300V. Put the propertygrid inside the panel with position -1,-1 and size 102,302.

Here is code from my project

PropertyGrid have two controls that need process.
+ doccomment is Document help.
+ gridView that display property value.

Those controls draw border rectangle with color ControlDark.

We need re draw rectangle with HelpBackColor and LineColor to make clear view.

    namespace Bravo.Bravo7.UI
    {
        public class MyPropertyGrid : PropertyGrid
        {
            public class SnappableControl : NativeWindow
            {
                private Control _parent;
                private MyPropertyGrid _ownerGrid;

                public SnappableControl(Control parent, MyPropertyGrid ownerGrid)
                {
                    _parent = parent;
                    _parent.HandleCreated += _parent_HandleCreated;
                    _parent.HandleDestroyed += _owner_HandleDestroyed;

                    _ownerGrid = ownerGrid;
                }

                protected override void WndProc(ref Message m)
                {
                    base.WndProc(ref m);

                    switch (m.Msg)
                    {
                        case (int)NativeMethods.WM_NCPAINT:
                        case (int)NativeMethods.WM_PAINT:

                            using (var g = _parent.CreateGraphics())
                            {
                                using (var pen = new Pen(_ownerGrid.HelpBackColor))
                                {
                                    var clientRectangle = _parent.ClientRectangle;
                                    clientRectangle.Width--;
                                    clientRectangle.Height--;
                                    g.DrawRectangle(pen, clientRectangle);
                                }
                            }

                            break;
                    }
                }

                void _owner_HandleDestroyed(object sender, EventArgs e)
                {
                    ReleaseHandle();
                }

                void _parent_HandleCreated(object sender, EventArgs e)
                {
                    AssignHandle(_parent.Handle);
                }
            }

            public class PropertyGridView : NativeWindow
            {
                private Control _parent;
                private MyPropertyGrid _ownerGrid;

                public PropertyGridView(Control parent, MyPropertyGrid ownerGrid)
                {
                    _parent = parent;
                    _parent.HandleCreated += _owner_HandleCreated;
                    _parent.HandleDestroyed += _owner_HandleDestroyed;

                    _ownerGrid = ownerGrid;
                }

                protected override void WndProc(ref Message m)
                {
                    base.WndProc(ref m);

                    switch (m.Msg)
                    {
                        case (int)NativeMethods.WM_NCPAINT:
                        case (int)NativeMethods.WM_PAINT:

                            using (var g = _parent.CreateGraphics())
                            {
                                using (var pen = new Pen(_ownerGrid.LineColor))
                                {
                                    g.DrawRectangle(pen, 0, 0, _parent.Width - 1, _parent.Height - 1);
                                }
                            }

                            break;
                    }
                }

                void _owner_HandleDestroyed(object sender, EventArgs e)
                {
                    ReleaseHandle();
                }

                void _owner_HandleCreated(object sender, EventArgs e)
                {
                    AssignHandle(_parent.Handle);
                }
            }

            public class MyToolStripRenderer : ToolStripSystemRenderer
            {
                protected override void OnRenderToolStripBorder(ToolStripRenderEventArgs e)
                {
                    //base.OnRenderToolStripBorder(e);
                }
            }

            public MyPropertyGrid()
            {
                base.LineColor = SystemColors.Control;
                base.ViewBackColor = Color.FromArgb(246, 246, 246);

                base.DrawFlatToolbar = true;
                base.ToolStripRenderer = new MyToolStripRenderer();

                var docDocument = typeof(PropertyGrid)
                    .GetField("doccomment", BindingFlags.NonPublic | BindingFlags.Instance)
                    .GetValue(this) as Control;

                new SnappableControl(docDocument, this);

                var gridView = typeof(PropertyGrid)
                    .GetField("gridView", BindingFlags.NonPublic | BindingFlags.Instance)
                    .GetValue(this) as Control;

                new PropertyGridView(gridView, this);
            }

        }

    }