How to implement background change when scrolling content in popup?

Question

css

Hello Dear Developers!
Is available here such:

The given window opens in popup. The right side will scroll and when a certain menu on the right reaches the middle, then the corresponding background should appear on the left side, for example, change smoothly.
Maybe there are already some ready-made scripts that implement this? Or ready-made examples on existing sites.
Thank you!

Answer 1

?
softwarespot.github.io/jquery-scrollspy