How to highlight menu items on scroll?

Question

css

Essence of the question:
There is a landing page, there is a menu, when scrolling the site it is necessary that the necessary link is highlighted in the menu! I installed the parallax plugin, in the code I see that everything works, the tag acquires the desired class when the section is scrolled, but if you set this class in css, nothing happens. Needs to be color coded.
An example is attached to a third-party site of a construction company, the menu is highlighted in blue when scrolling through the desired section.

Answer 1

https://codepen.io/rishabhp/pen/aNXVbQ
The point is to keep track of the active section, but you can set any styles.