[CommandMethod("GetBkClr")]

        public void GetBkGndColor()

        {

            // Access the Preferences object

            AcadPreferences acPrefComObj = (AcadPreferences)Application.Preferences;

            uint clr = acPrefComObj.Display.GraphicsWinLayoutBackgrndColor ;

            ed.WriteMessage(UIntToColor(clr).ToString());

        }

        [CommandMethod("SetBKClr", CommandFlags.Session)]

        public void SetBkGroundColor()

        {

            // Access the Preferences object

            AcadPreferences acPrefComObj = (AcadPreferences)Application.Preferences;

            // Use the CursorSize property to set the size of the crosshairs

            acPrefComObj.Display.CursorSize = 100;

            System.Drawing.Color bkClr = Color.FromArgb(0, 255, 255, 255);//white, do not use known color, use Argb instead.

            //acPrefComObj.Display.GraphicsWinLayoutBackgrndColor = ColorToUInt(bkClr);

            acPrefComObj.Display.GraphicsWinModelBackgrndColor = ColorToUInt(bkClr);

        }

        private uint ColorToUInt(Color color)

        {

            return (uint)((color.A << 24) | (color.R << 16) |

                          (color.G << 8) | (color.B << 0));

        }

        private System.Drawing.Color UIntToColor(uint color)

        {

            byte a = (byte)(color >> 24);

            byte r = (byte)(color >> 16);

            byte g = (byte)(color >> 8);

            byte b = (byte)(color >> 0);

            return Color.FromArgb(a, r, g, b);

        }