Modify CSS from Form Display Rules
Within Form display rules you can now set rules when the condition is met to add or remove CSS classes to other inputs.
For example, in the example below when Status is equal to For Sale, a new CSS class called "required" will be added to the "Listing Name" field:
You can do the same by removing a CSS class from any other field.
To take this further, you can use the Hide or Show options then select he CSS Selector option with the CSS classes or IDs to either show or hide those elements:
Keep in mind, that this will work with elements even outside of the form. Any CSS on the page is fair game, so be careful to break your app.