如何在C#winforms中更改未使用的空格选项卡的背景颜色？

using System;
using System.Drawing;
using System.Windows.Forms;

public class CustomTabControl : TabControl
{
    public CustomTabControl()
    {
        SetStyle(ControlStyles.UserPaint, true);
    }

    protected override void OnPaint(PaintEventArgs e)
    {
        base.OnPaint(e);
        Graphics g = e.Graphics;
        Rectangle clipRect = e.ClipRectangle;
        SolidBrush backColorBrush = new SolidBrush(Color.Red); // 更改此颜色以设置所需的背景颜色

        g.FillRectangle(backColorBrush, clipRect);
    }
}