How to change the color of “time” in the top panel?

[ironfoot]

Panel fonts color

I'm using a theme where the color of the fonts on the panel are dark and they do not contrast the panel's background which is also dark. [Screenshot at 2020-05-24 16-59-34] I understand that we have to edit/create a gtk.css file in ~/.config/gtk-3.0/ What should the contents of this file be to set the font color white?