The high contrast mode is a mode introduced in Windows 8, to compensate for the discontinuation of support for the classic theme for visually impaired users. For Win32 programs, it uses the Aero Lite visual style in a particular mode (much like Aero's "Dark" mode), which forces rendering by Win32 color settings. In UWP/WinUI apps, it forces the use of Win32 color settings, which is the only way, since UWP apps don't work with the classic theme. The parameters used are only certain colors, less than with the classic theme. Tomorrow I will post the links to the Microsoft documentation on this subject, as well as the research I have done on the parameters used, and the results on the Win32 and UWP type elements and for the Windows 10 taskbar and start menu (I don't is not sought for Windows 8 and 11).

It seems to me that the result Win32 programs are almost between Windows 8/10/11, but much less the UWP type elements.