If one enables the dark color scheme on Windows 10 then the tooltips are hard to read because the text color used for the tooltips is way too dark.

This seems to be a bug in Qt's Windows Vista style which tries to use the same colors for tooltips as Windows, but it fails to get the correct color if the dark color scheme is enabled. I'm not sure if Qt is to blame or the Windows API which returns the wrong color, but it doesn't really matter. The problem doesn't occur if one forces the fusion style.

The problem probably doesn't occur with Qt's new Windows 11 style (introduced with Qt 6.something) because it seems to use different code for the (tooltip) colors.

This has also been reported at https://bugs.kde.org/show_bug.cgi?id=481772