[Dark Mode] CheckBox/RadioButton text with FlatStyle 'System' is hard to visible after enabled SystemColorMode.Dark

[Olina-Zhang]

.NET version

9.0.0-rc.1.24418.2 + private dlls built from winforms repo main branch

Did it work in .NET Framework?

No

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

This is a new feature Dark Mode: #11857

Issue description

CheckBox/RadioButton text with FlatStyle 'System' is hard to visible after enabled SystemColorMode.Dark

Steps to reproduce

1. Create a WinForms .NET application with RadioButton/CheckBox control, set RadioButton/CheckBox's FlatStyle == System
2. Enable DarkMode by Application.SetColorMode(SystemColorMode.Dark) in Program.cs file
3. Run the application to observe

[AraHaan]

It would be nice if Application.SetColorMode(SystemColorMode.Dark) can be done outside of Program.cs as well like if you want the application itself to have a Dark or Light mode switch directly inside of it.

[AraHaan]

I have also discovered that when I use Flat for FlatStyle with Dark Theme that the control Boarders other than the context menus are white and not this color for which I expect them to be: Color.FromArgb(28, 32, 38) For now in my application I have to manually draw them myself over the color that is used in the Paint event for those controls.

Please consider a patch for this that way application developers can get this boarder color for free without needing to dive deep into painting themselves in their own winforms application.