Change button colors as slides change

Sorry about that, I will elaborate more.
Currently I have a slideshow on autoplay. Like any slideshow, they change automatically after 5 seconds to the next slides.
I also have buttons the the left of the slides, where if someone hovers over the buttons, the slideshow automatically goes to the corresponding slide. Please see setup below. As you can see, slideshow on the right, buttons on the left.

However, currently when the slideshow autoplays, the buttons on the right do not change color. They stay the dark green. Its hard for visitors to see which button corresponds to which slide.

I would like to see if its possible where when the slideshow changes to the next slide, the button on the right changes to a specific color.
For example, if the slideshow is on the contact human resources slide (as it is on the above screenshot), i would like the “Contact Human Resources” to be a lighter green color and all other buttons remain dark green. And then if the slideshow autoplays to the next slide, I would want the corresponding button to be light green while all other buttons remain the dark green color.

Two screenshots below, from another site, show what I mean. As you can tell, the button color changes to match the slide that is being shown. This is what I want to do.

thank you for your help!