ColorScheme-ButtonText is not set
Some icons, mostly former Plasma theme icons, use ColorScheme-ButtonText. However KIconColors doesn't set this, so it will always be the default black-ish.
We have ColorScheme-Text, which is a slightly different black-ish by default. Is there a meaningful difference?
If yes we need to wire up ButtonText in KIconColors
If no we need to port usages to Text and drop ButtonText from the stylesheets