Trying to make my navigation change color with blend modes

Hi Everyone!

I am trying to make my navigation links change color on dark backgrounds for hours now.
I implemented a custom html block with a style tag and: mix-blend-mode: difference;
But I don’t seem to find how to get this working.

What I want to achieve is that the black navigation changes white on black backgrounds and the other way around black on white backgrounds.

The read only link is this one: Webflow - SM-2021

Hope someone can point out what I am doing wrong - thanks in advance!

Here is my site Read-Only: LINK
(how to share your site Read-Only link)