There should be white text on a black background in the Quick Reply or Fully Reply text boxes, when using the forum's default stylesheet, and assuming you don't have your browser overriding the text colour (try a different browser, if convenient).
You can click 'My Stuff' in the top menu bar, then 'Edit Preferences' to check or change 'Your preferred stylesheet'.
If that doesn't help, post in the
About this website forum.
