Text highlight color (i.e., change color from black to a different color) doesn't seem to work

I want to change the text color in a Text field.

There is an example in the manual here:
https://labelstud.io/tags/text.html

But though the font color should be red, it is not. It remains black. I tried it with some other color as well, nothing changed.
Am I missing anything? Seems weird for me that a formal example doesn't work (you can also see that it doesn't work in the preview\background).