I have seen that with the oncoming qt5 / kf5 it will be possible to have the color scheme set individual per application. Then I think it should also be possible to have the color scheme as a per activity setting. So please respect/support per activity color scheme settings in the oncoming kf5 activities.
I have no idea what is going on with the per-app colour scheme stuff. If it ever gets released, this might be a good idea. Marking as 'later'.