So *something* changed in Plasma 6.5 and/or Breeze and suddenly the brightness/colors of my screens feel *off*

Like it's not super jarring, but it's just different enough to be noticeable.

Also I think something changed in the compositing layer because behind-window blur also looks different.

@lethalbit The blur effect was merged with the contrast/saturation effect and I have yet to find a way to turn the latter two off. Which is a shame because in HDR mode blur is now literally unusable because of https://bugs.kde.org/show_bug.cgi?id=502651
502651 – The background of translucent widgets is brighter than SDR white in HDR mode

@lethalbit FWIW Plasma 6.5.1 seems to have fixed the excessive brightness! The saturation effect is still quite noticeable but now it doesn't destroy readability any more.