To visually portray that, Ralph Horsley depicts a faerie that has become twisted and savage, like a boggart. Let's blow the art up so we can get a good look at it:
But what would this faerie have looked like before it changed color? It would have been less savage, and its mount would have looked calmer. And of course, its colors would have been different. In short, it would have looked like this:
Clearly, someone cast the color-changing spell on Glen Elendra Liege!