Yeah, afaik MacOS can do it too.

ICC profile is built-in in memory of my laptop screen?

Yeah. Surprisingly, nearly every display comes with somewhat accurate color information in its EDID.

Even Windows can’t do it

Afaik they did actually implement something in this direction in Windows 11, but it’s not exposed in a user friendly way yet.

There is no saturation slider, though. I’ve seen it on some screenshots.

It’s currently always shown if the built in color profile, HDR or an ICC profile is used. IIRC it wasn’t visible with the color profile in some older version of Plasma though, maybe that’s why you don’t see it.

Afaik Youtube is doing that, not Pulseaudio, and there’s nothing that can be done about it.

what about color managed apps?

Colord isn’t running and no icc profile is set on Xwayland, so they should assume sRGB as the target and be fine.

Do note that nothing is applied “to the full screen”, color management is done on each individual surface during compositing. If an app uses the color management protocol to use some colorspace, it gets taken into account.

Are you sure you can affect saturation system-wide with color profiles?

Yes, I wrote the relevant code in KWin.

Because in Gnome it’s not possible.

That’s because Gnome’s color management support is still limited, they don’t apply the full ICC profile yet.

Sounds like you want color management, not just arbitrary saturation changes.

Install KDE Plasma, select the “built-in” color profile, and you’re done, no more oversaturated colors. If you want to test how it looks, just use a live boot.

Why would you run it in Proton? It’s a native game.