This is starting to happen with things like google material and similar UI libraries that try to standardize appearances across devices. It isn't as granular as you are asking but I actually like that aspect. Delegating design and display to the browser isn't ideal for a lot of reasons. I would like to exercise control over how my content is displayed and regularly load in reset sheets for css. Display is something delegated to a framework not a browser (my opinion).
I think that <something/> should be in charge of handling representation and we are seeing that with ui frameworks that standardize displays across devices and applications.
> background-color could be completely replaced by a 'contrast' tag
What? There are many different colors on websites and users are lazy. Also, css should ideally be for styling not positioning, but it is one of the only options right now.
It might be a strange (and incomplete) thought but how I see it is that the browser would deduce the color. Contrast would be relative to text. For example the panel has a contrast of 0.8, so the browser should chose a color which is readable according to the text color if we would put both on the same panel. This color could be picked from the OS design. It does not mean that it would be ugly tough since you can use pretty good designs and colors, the web would just look much more consistent.
i am just going to punt because this still isn't landing for me. Maybe I am just mischaracterizing you, but it seems like you are either frustrated building things with outdated tools, or you want more control as a user. If it is the former, we are at the top of a funnel right now and we will start to see much better tools become improved and a few winners will emerge. If you want more control over your sites as a user you would probably have to force the css to either not load, or override it with your own scheme.
it's just, when you say color, it isn't that easy. There are tons of screen sizes and even as minimal as hacker news is has at least 4 colors, so I am not sure what would happen on a site like fast company with many different colors. An OS/Browser couldn't manage that because no one would agree. Ok fine I didn't punt.
I think that <something/> should be in charge of handling representation and we are seeing that with ui frameworks that standardize displays across devices and applications.
> background-color could be completely replaced by a 'contrast' tag
What? There are many different colors on websites and users are lazy. Also, css should ideally be for styling not positioning, but it is one of the only options right now.