How to change the combobox's scrollbar's background color

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

namespace YourNameHere
{
    public class AdvancedComboBox : Panel
    {
        private System.Windows.Forms.TextBox textBox1 = new TextBox();
        private System.Windows.Forms.Panel panel1 = new Panel();
        private System.Windows.Forms.ListBox listBox1 = new ListBox();

        public AdvancedComboBox()
        {
            InitializeComponent();
            listBox1.Visible = false;

            listBox1.Items.AddRange(new object[] { "Apple", "Pear", "Orange", "Grape", "Lemon", "Lime" });
            panel1.BackgroundImage = setButtonOff();
        }

        private void InitializeComponent()
        {
            this.Controls.AddRange(new Control[] { textBox1, panel1, listBox1 });
            this.panel1.Location = new System.Drawing.Point(128, 59);
            
            this.panel1.Size = new System.Drawing.Size(15, 20);            
            this.panel1.MouseDown += new System.Windows.Forms.MouseEventHandler(this.panel1_MouseDown);
            this.panel1.MouseLeave += new System.EventHandler(this.panel1_MouseLeave);
            this.panel1.MouseHover += new System.EventHandler(this.panel1_MouseHover);
            this.listBox1.FormattingEnabled = true;
            this.listBox1.Location = new System.Drawing.Point(28, 79);
            this.listBox1.Size = new System.Drawing.Size(115, 95);
            this.listBox1.SelectedIndexChanged += new System.EventHandler(this.listBox1_SelectedIndexChanged);
            this.listBox1.MouseLeave += new System.EventHandler(this.listBox1_MouseLeave);

            this.textBox1.Location = new System.Drawing.Point(27, 59);            
            this.textBox1.Size = new System.Drawing.Size(100, 20);
            
        }

        private void listBox1_MouseLeave(object sender, EventArgs e)
        {
            listBox1.Visible = false;
        }

        private void listBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            textBox1.Text = listBox1.SelectedItem.ToString();
            listBox1.Visible = false;
        }
        private void panel1_MouseDown(object sender, MouseEventArgs e)
        {
            if (listBox1.Visible)
            { listBox1.Visible = false; }
            else { listBox1.Visible = true; }
        }
        private void panel1_MouseHover(object sender, EventArgs e)
        {
            panel1.BackgroundImage = setButtonOver();
        }
        private Image setButtonOff()
        {
            string base64String = "iVBORw0KGgoAAAANSUhEUgAAABIAAAASCAIAAADZrBkAAAAABmJLR0QA/wD/AP+gvaeTAAAACXBIWXMAAA7EAAAOxAGVKw4bAAAARUlEQVQokWP8//8/A4ng1duPjGRoY2BgYCJDz6g2bIAFqygjIyOmIHJUYbcNMzLRRHA6Elkdpin4/AZRjTUZjSYuamkDAD0zINGCHX3yAAAAAElFTkSuQmCC";

            byte[] base64byte = Convert.FromBase64String(base64String);
            MemoryStream ms = new MemoryStream(base64byte);
            return Image.FromStream(ms);
        }

        private void panel1_MouseLeave(object sender, EventArgs e)
        {

            panel1.BackgroundImage = setButtonOff();
        }

        private Image setButtonOver()
        {
            string base64String = "iVBORw0KGgoAAAANSUhEUgAAABIAAAASCAIAAAGuqymWAAAABGdBTUEAALGPC/xhBQAAAAZiS0dEAP8A/wD/oL2nkwAAAAlwSFlzAAAOxAAADsQBlSsOGwAAAAd0SU1FB9sDGQA2Npg6IGUAAAB0SURBVCjPY1z54z8DAwMDAwMTAwNDOAcjAwMDI1wMxoJQjCgUHDAxoAIUeSYsKtFtQVeGbgE+y/DJQewhbCZOuQd/cdunwEySW5ABC1YXQhzBhMZHZlArXIgNazKNHDTaWHBJIAc7cgATFSThHNgVDImQBAAVrjj7k1ImuAAAAABJRU5ErkJggg==";

            byte[] base64byte = Convert.FromBase64String(base64String);
            MemoryStream ms = new MemoryStream(base64byte);
            return Image.FromStream(ms);
        }
    }
}