New feature: `AccentColor` reflects the computed value of `accent-color`

[LeaVerou]

Specification

https://drafts.csswg.org/css-color/#css-system-colors:~:text=To%20maintain%20consistency%20with%20widget

See also: w3c/csswg-drafts#5900

Description

To maintain consistency with widget accent color styling, AccentColor takes its value from accent-color, unless Forced Colors Mode is enabled. AccentColorText takes its value from the contrasting foreground color to AccentColor as is described for widget accent color styling.

Documentation

N/A

Browser support

https://chromestatus.com/feature/6207138742534144

None AFAIK (testcase)

Depends on #4284

[ddbeck]

Depends on #4284

I think this is correct, at the moment. Sorting that out will inform how we handle this feature. I'll come back to names, IDs, and descriptions when that's resolved.

But that's not going to stop me from speculating a little here: I expect that this feature will sit at the intersection of two predecessor features: an AccentColor feature (for the system color value, to be minted) and the accent-color (source, dist) CSS property feature.

If that's the case, then this might be a candidate for quick merging (see also: #4083) into one of those predecessor features (I think accent-color). Since neither of the predecessor features are Baseline (as I suspect might be the case, given #4284), then we might understand this behavior to be part of one of those predecessor features, especially if we get consistent behavior across all three notional features in a short time frame.