How to add blur to my nav menu?

So I followed a few tutorials and was able to add a blur effect to my NavBar (on top, although it’s hard to see in the screenshot). But how do I add the blur effect to the nav menu (in red) which opens in mobile versions of the website?

As you can see, right now I have it as red. I’d like to add the blur effect as on my navbar here instead of the red. The blur effect is easier to see in my preview link. Any help would be greatly appreciated.

Here is my site Read-Only: Webflow - Deependu Ajish | Portfolio 2021