With my current (and favorite) theme the Unity panel is black text on a black background. Is there a way to set the font color in Unity or the theme somehow?
The panel text uses the color defined by the theme's
Note, that this doesn't affect the home button and indicator icon color. For that you'd have to change the icon set used by your theme (in Appearance Properties → Theme tab).
Use GTK Theme Preferences...
Also add your current panel background color when you change panel text color. Install gcolor2 for the old style color picker to copy your panel color or look in your theme.