procedure TForm1.CheckBox1Paint(Sender: TObject);
var
  CheckBox: TCheckBox;
  Rect: TRect;
begin
  CheckBox := Sender as TCheckBox;
  Rect := CheckBox.ClientRect;

  // 清除背景色
  CheckBox.Canvas.Brush.Color := clWhite;
  CheckBox.Canvas.FillRect(Rect);

  // 绘制纯色复选框
  CheckBox.Canvas.Brush.Color := clBlue;  // 设置复选框的背景颜色
  CheckBox.Canvas.Pen.Color := clRed;    // 设置边框颜色
  CheckBox.Canvas.Rectangle(Rect);

  // 绘制勾选标记
  if CheckBox.Checked then
  begin
    CheckBox.Canvas.Pen.Color := clWhite;
    CheckBox.Canvas.MoveTo(Rect.Left + 4, Rect.Top + Rect.Height div 2 - 1);
    CheckBox.Canvas.LineTo(Rect.Left + Rect.Width div 2 - 1, Rect.Bottom - 4);
    CheckBox.Canvas.LineTo(Rect.Right - 4, Rect.Top + 4);
  end;
end;