System colors are still badly implemented in #CSS in most #browsers other than #Firefox on macOS.
AccentColor and AccentColorText are MISSING in #Opera and #Edge (Blink-based) but ARE (wrongly) implemented in #Chrome (Blink-based).
SelectedItem and SelectedItemText are implemented correctly (Edge,Opera,Chrome) under color-scheme: light, but not under color-scheme: dark, falling back to Chrome's AccentColor tint.
ActiveText is red in Firefox, Chrome and Edge, but blueish (like LinkText) in Opera.

Left to right: Chrome, Opera, Edge, Firefox.

System Settings:
Appearance: Dark
Accent Color: Green
Highlight Color: Green

Also F-ing weird (but somehow also completely logical) is that #Safari (by #Apple, the people who created the appearance panel) doesn't use macOS' Appearance settings. Not the Accent Color and not the highlight color. How #Chrome does better on Apple's own F-ing OS is beyond me.

Left to right: Chrome, Safari, #Firefox.

Chrome supports Highlight/HighlightText AND SelectedItem/SelectedItemtext (in color-scheme light) while Apple themselves are like "dumb feature, never used it"

Ah. Found the weirdness about Chrome vs Opera and Edge. With the flag "Experimental Web Platform features" disabled you get:
- correct Highlight and HighlightText (in the accent color of macOS)
- correct SelectedItem/SelectedItemText ONLY IN color-scheme: light (in the accent color of macOS)
- NO AccentColor/AccentColorText whatsoever.

With the flag enabled you get:
- SelectedItem/SelectedItemText STILL WRONG in color-scheme: light
- AccentColor/AccentColorText WRONG in both color-schemes.

There is no difference in Safari 18.5's Technology Preview 222

Can't download Safari 26's Technology Preview since apparently to update a browser you need to update your macOS to an unstable beta of Tahoe (which is beyond idiotic. the Apple we know and love) but I reckon there will no differences. Apple's browser is kinda dead and nothing every truly changes. My hope at this point is for Servo and Ladybird to become browsers that actually implement full specs instead of half-assing everything.