I'm struggling to post to this list, so hopefully this will work.

Harriet Bazley wrote:
> Unfortunately I'm pretty sure Netsurf doesn't offer any mechanism to
> force HTML pages to change their colour scheme.  It doesn't offer all
> that many customisations anyway (you can't even tell it not to load
> images, so far as I'm aware).   I think it was mainly written to be
> small and fast, rather than highly flexible.

There is a media query which allows a web browser to pick up the preferred colour scheme (light mode/dark mode) from the OS (or the browser itself).  NetSurf does not implement this, so everything defaults to light mode.

That would help with sites which support dark mode (via the media query or otherwise), however still leaves the rest of the web in light mode.

You can change the default CSS but it is only going to help if the page itself doesn't specify colours.

If the page specifies colours then they will be used by NetSurf - there's no way of overriding them (beyond light mode/dark mode - and even then you're still using colours specified by the page).  I'm not sure how you'd even go about implementing this.