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;