I'm having the same issue--can't see black text against highlighted item in drop down list.
In reading about the issue, I've found no suggestions of a way to change this within FM. However, the color of the highlight is set at the system level. So, if you've chosen light blue within the General Settings of System Preferences, FM intensifies it to the darker blue (which makes black text unreadable). For now I changed the system highlight to gray. FM intensifies that to a darker gray, but I can now see the black text against the highlight.
I'd love to hear a better answer!
Thanks for the input.