I never had 100% luck with Windows 10 themes, unless that is the up and coming "Dark Explorer Mode",
which I would expect to be more compatible with menu programs.
Hmm, so you have got the Classic Skin with the rounded corner selector buttons.
Does switching to "Solid color selection" buttons (in the skin options), make the text white, instead of black?
If so you might be able to edit the skin text color from:
Main_text_color=#000000,#000000,#7F7F7F,#7F7F7F
to
Main_text_color=#FFFFFF,#000000,#7F7F7F,#7F7F7F
or
Main_text_color=$SystemMenuText,#000000,#7F7F7F,#7F7F7F
If that does not work, try a different skin.
If the dark theme is using High Contrast settings, see if your theme is in the dropdown list.
You might be able to change the menu text color in those Windows color settings boxes for that dark theme.
If it is a WindowBlinds theme, WindowBlinds overrides everything and is hard to change.
Try a different theme that is made for a particular Windows 10 version?
That's all I've got.