Button to switch the user’s dark mode browser preference?

I want to provide a “dark mode” switch on a website. That would be easy by using some CSS.

But then: Modern browsers can already tell the website that they want to use a dark mode (prefers-color-scheme). And I can also react to that via CSS.

@media (prefers-color-scheme: dark) {
    html {
        filter: grayscale(0.75) invert(1) contrast(1);
    }
}

My problem is: I do not want these mechanisms (button on the website and browser preference) to collide. And I need the button on the website, because many users don’t know that their browser can change the preference.

Is there any mechanism that would allow a website to provide a button that would change the browser preference?

I fully understand that you would usually not want to allow websites to do something like “change my preferences”, however, it seems like a good idea regarding the prefers-color-scheme.