I wouldn't necessarily say that Zorin OS is easy to customize. Keep in mind that the whole appearance already is a customization layer added to make it look that way. There's even a warning about this in the help page:
This isn't to say that you can't modify it... but I do wonder if something has changed in how the shell works with the current version of Gnome available in Zorin OS.
Did you install or changed anything else that might affect the font color?
For reference, here's an example of a MacOS lookalike in Zorin OS: