The Breeze (Dark) panel accents (blue) are hardcoded into the [[ https://i.imgur.com/IlpqizT.png | tasks.svgz file ]],Light/Dark desktop themes' highlight, hover, positive, neutral and negative colors are set in their `colors` files. If those colors came from system colorscheme, then the user could customize the look of their desktop even more, without needing to make a custom desktop theme. if it was based on the [[ https://techbase.kde.org/Development/Tutorials/Plasma5/ThemeDetails#Colors | color scheme ]] then the user could change the accent color by changing a setting.The BackgroundAlternate, BackgroundNormal, ForegroundInactive and ForegroundNormal colors would remain since the Breeze Light/Dark desktop themes are meant to force a light or dark color for widgets and panels.