Shell palette colors in the merged shell take a Commons.Color name after Qt 6.12
Pull request 14553 merges a shell change that names palette colors Commons.Color, after Qt 6.12 introduced a Color type that shadowed the shell palette.
The pull request says a Quickshell rebuild against Qt 6.12 left those colors undefined and broke the desktop presentation. The palette is the set of colors the shell uses for the bar and for menus. The merged shell imports that palette as Commons and uses the prefix, including on the bar.
The pull request says third-party plugins need the same prefix. Their QML files have their own import scope, so an unqualified Color can still point at Qt's type. Imports for Style, Util, and Border stay as they were.
David Heinemeier Hansson opened and merged the change. He wrote that the running bar and the Defaults menu were checked on Qt 6.12, and that the full shell suite is not reported as passing because of sandbox, display, and unrelated failures.