How do I make a sticky navbar change background colour when I reach the top of the page?

Design help Animations & Interactions
1

I’d like my nav bar to work like this: https://www.altruus.com/

As you can see when you scroll back up to the top of the page, the nav bar changes background color (to 0% opacity).

Any help would be really appreciated!

Thanks,

Frankie

Here is my public share link: LINK
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