[Accessibility] [HC] The little triangle of "toolbar options" button in ToolStrip is hard to visible when focusing on it

[Olina-Zhang]

.NET version

8.0.100-alpha.1.22451.15

Did it work in .NET Framework?

No

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

No, not a regression issue

Issue description

The little triangle of "Toolbar options" button in ToolStrip is hard to visible on Windows 11 high contrast themes and Windows 10 high contrast black/white themes

Windows 11 HC Aquatic/Desert/Dusk/Night Sky testing results:

Windows 11 default theme:

Windows 10 HC black/white/#1/#2 testing result:

Windows 10 default theme:

Steps to reproduce

Sample application: WinFormsApp9.zip

[merriemcgaw]

That glyph should come from a standard System color. It's also pretty clear we don't meet contrast minimums here either.

[Amy-Li03]

Verified this on .NET 8.0 latest build: 8.0.100-alpha.1.22552.11, issue was fixed on Win10 and Win11 OSes.