Hi Tony,
I think you already found this post: https://forum.mendix.com/link/questions/85644 as you mentioned that there are CSS classes that will do what you are looking for. Among the answers there, you’ll also find a JS solution.
PS: I see that you are using Mendix Version 8.4.2 – Have you heard about Calypso? No need for gulp, Koala or installers. If you have not tried it yet, give it a shot. It’s pretty nice and easy to work with actually :) https://docs.mendix.com/howto/front-end/calypso