So is this basically adding the ability to (among other things) let server side applications know about color scheme, so the server side code can render a dark page?
What I'm not understanding from the page is: it seems that the Client Hint 'dark mode please' header is only sent in a second or a subsequent request to the server, only after the server has said, 'I will accept your Client Hints'. Isn't it too late by then, since the first response contains the full HTML output required. Or there must be some property of "HTTP/2 + TLS 1.3 + ALPS" that is self evident but not to me.
