Yesterday I was asked if states can have color only along borders. We already had the Halo effect, but it was not possible to use it separately from states fill. Now, after about a day of refactoring of a very messy code, the functionality is ready. Now it should be simpler to style the states layer.
To show one of the possible solutions, I have added a new style set - Watercolor. It's build around this state border color idea, but I've included some other ideas as well. The most doubtful component here is white shadowed labels with somehow jokey font, but, as always, you are free to restyle the labels.