.NET version

.NET SDK 10.0.100-rc.1.25410.103

Did it work in .NET Framework?

Not tested/verified

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

Yes, occurs after the PR change: #13747

Issue description

In dark mode, the divider line between the UpButton and DownButton in bothDomainUpDownand NumericUpDown controls becomes invisible when the mouse hovers over the buttons or when they are clicked. This results in a lack of visual separation between the buttons, negatively impacting the user interface's clarity and usability. It doesn't repro in classic mode.

Just run app:

Hover the mouse over the UpButton and DownButton, or click on them:

Steps to reproduce

1. Create Winforms .NET application with targeting .NET 10
2. Add DomainUpDown/NumericUpDown control in form designer
3. Set app under Dark mode in program.cs file:

#pragma warning disable WFO5001
      Application.SetColorMode(SystemColorMode.Dark);
#pragma warning restore WFO5001

4. Build and run app
5. Hover the mouse over the UpButton and DownButton, or click on them.