Menu position fixed and background color to white when scrolling down

Sir,
How to do:
I would like transparent background on my menu by default + white font color (or other color), and when the user scrolling down, the background color menu become white + text black (or other color) and the menu stay fixed.
All the theme I already used get this possibilities, I'm very surprised that is not possible with NP?
And also the possibility to resize element like logo on scrolling down (see example below)

Example of what I would like (menu transparent at start and opaque or with transparency and fixed on scrolling down):
https://empire.madebysuperfly.com/

Last edited 09 January 2021 by erikdenice