Please try the following JS code:

jQuery( ".wpf-search" ).click(function() {
   jQuery("#wpforo #wpforo-wrap .wpf-search i").css("color", "#00070b");
});

Please note the red marked value can be changed.

The code should be added in the current active theme JS files.

Here is an instruction on "How to Add Javascript  Without Breaking Your WordPress Site": https://www.collectiveray.com/add-javascript-to-wordpress

I would like to chage the Fa search icon color when the search form is in use. I used ':focus' to target the search form text input field when it is open, but that isn't working for the FA icon.

Does anyone have any idea how I can set the FA icon color differently, depending on whether the search form is visible or not? I appreciate the guidance.

.wpf-search input:focus