Hello tridy,
Looks like that happening cause that program you're using
have some hard coded parts, this mean that it's ignore some
skinning aspects and use it's own setting (like that text color).
In that specific case, you set the background as black and
the text as white, the combobox use the same color from the
window text (white as you set) and have it's own background graphic
that is white then you're having white text over white background.
The way to fix it is setting that text as black or a similar dark color (and the background
may change to a color where you can read black text).
