Conditional formatting on dropdown menus

Hey there! First post here.

I’m trying to build a form that starts with two dropdown menus. The thing is that the second’s choices depends on the first’s answer.

I tried to do that with conditional formatting using “When dropdown A’s value is bananas” and using the option “Choices (…)” on the "Select a property to change when true"menu. It hasn’t worked.

Any ideas on how to do it?

Something like this:
If my user chooses football (the first item in my sports list), then I change the color of the leagues dropdown to green.

Screen Shot 2020-07-18 at 12.18.28 PM

In this case you previously had a list called Sportss and pointed to an item in that list, correct? Maybe I can’t do that correlating both dropdown menus directly.