I wanted something about that difference to show in the cover, hence the white background. The covers of the Innocence Cooper series each reflect one of the active powers witches can have in the series. Book #1 shows fire, #2 ice, #3 the purple electricity pulses. In some ways those powers tie to the stories - some more strongly than others.
Book #4 shows dark energy, which is a rare and dangerous gift that is granted by the dark masters instead of the spirits who gift ever other power. The dark masters themselves will make an appearance in book #4, and we will finally know why they favour who they favour.
Enough of that. Cover:
(All covers in the Innocence Cooper series have been designed by Rebecca Frank, http://bookcovers.rebeccafrank.design/)