Currently we have the Ambience QML theme and a similar Ambiance HTML5 theme for local HTML5 applications. We don't have a mechanism for changing the theme and having those changes respected across the range of apps that the device can have. We don't have any mechanism for remote web applications to reference the current device theme. For accessibility or aesthetic reasons a user might choose a different base font size, different primary and accent colours etc. If all the apps use a local copy of the ambience theme then they are going to be inconsistent. It should be possible for the core phone to expose it's current theme for apps to use. If we can serve up the theme in a context that can be shared to remote web applications then we have an opportunity for a much more consistent visual experience than other platforms can achieve.