In #5433, we resolved to remove the forced value from prefers-contrast.

I think the logical conclusion of this, is that there is no more use case for a catch-all (prefers-contrast) that isn't either explicitly low/less or high/more, because I can't come up with a use case where you would want to change something in both low/less and high/more contrast modes and also would NOT WANT apply when forced colors is active, too. If there are still such use cases, they should be pretty rare, and probably warrant an explicit (prefers-contrast: more) or (prefers-contrast: less).

Because of this, I suggest we drop (prefers-contrast) as a boolean flag, while keeping both (prefers-contrast: more) and (prefers-contrast: less); instead of the removed boolean flag, we add a new feature query that indicates that a color complexity reduction might be a good thing. This media query would apply as a superset of a couple of other preferences, some of which are not possible in all operating systems and authors might forget if they have to mention them all explicitly, but have similar implications for website authors, such as:

• high contrast
• low contrast
• forced colors
• reduced transparency
• ...

Proposal: (reduced-colors) boolean media query.

The proposal would be something along the lines of (reduced-colors) (name to be appropriately bike shedded).

The media query would be a syntactic sugar for:
(prefers-contrast: more) or (prefers-contrast: less) or (forced-colors: active) or (reduced-transparency)

Additional questions:

Optionally we could replace (forced-colors: active) by it, by allowing two sub-values, like (reduced-colors: forced) vs (reduced-colors: optional) where optional would match all cases that are not forced-colors.

Does that seem reasonable?

cc @tabatkins @frivoal @cookiecrook