ComboBox drop-down button incorrectly uses BackColor under VisualStylesMode.NET11

[Olina-Zhang]

.NET version

.NET 11 SDK build: 11.0.100-rc.1.26380.103

Did it work in .NET Framework?

Not tested/verified

Did it work in any of the earlier releases of .NET Core or .NET 5+?

Not support, new feature of #14792

Issue description

When VisualStylesMode is set to NET11, changing the BackColor of a ComboBox also changes the background color of the drop-down button.

Under VisualStylesMode.Classic, only the editable portion of the control uses BackColor; the drop-down button continues to use the system button color.

Steps to reproduce

1. Create a WinForms application with targeting .NET11.
2. Set Form's VisualStylesMode to NET11.
3. Add a ComboBox.
4. Set:
   comboBox1.BackColor = Color.Pink;
5. Run the application

WinFormsApp1.zip