function RgbToGray(RGBColor : TColor) : TColor;
     var
       Gray : byte;
     begin
       Gray := Round((0.30 * GetRValue(RGBColor)) +
             (0.59 * GetGValue(RGBColor)) +
             (0.11 * GetBValue(RGBColor )));
       Result := RGB(Gray, Gray, Gray);
     end;

     procedure TForm1.FormCreate(Sender: TObject);
     begin
       Shape1.Brush.Color := RGB(255, 64, 64);
       Shape2.Brush.Color := RgbToGray(Shape1.Brush.Color);
     end;