Although testing with other color schemes there is clearly an underlying difference in the code between how the Kirigami separator determines the color and Breeze:

If someone could point me to the place in Breeze that does this I could try to replicate the exact thing.

Maybe we should have the Theme provide the opacity somehow?

You can look at the kde:breeze repository for the kstyle and others.

Widgets style: https://cgit.kde.org/breeze.git/tree/kstyle/breezehelper.cpp#n76

Qtquickcontrols style is pretty inconsistent and uses 0.2, 0.25, 0.3 alpha and either color mixing or transparent text color.

+1 visually, but I agree that the Breeze Widget theme should be the part that provides the theming, if possible.

In D22106#487287, @mglb wrote:

Widgets style: https://cgit.kde.org/breeze.git/tree/kstyle/breezehelper.cpp#n76

Qtquickcontrols style is pretty inconsistent and uses 0.2, 0.25, 0.3 alpha and either color mixing or transparent text color.

Hmm I tried to copy that code and it also produced good results with Breeze and Breeze Dark, but could be way off with other themes.

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