For lighting, anything suitably dark and spooky will do the trick here. At minimum, set Sun to Midnight, but you'll probably want to go beyond that. Aero Pines recommends using the "Ghost" Windlight setting.
My witch gravitated to the cauldron which was bubbling and glowing green, so I switched to "Gelatto" and pretty much kept it there for the rest of the shoot, modifying the setting slightly with different camera changes. (I believe "Ghost" and "Gelatto" are settings that come with each viewer, so they should both be in your list. "Ghost" is similar to "Foggy" but darker-toned, while "Gelatto" is darkly clear with chartreuse and green tones.)
Start with Midnight or a setting like Ghost, but do experiment from there. The concept of Halloween witches can be expressed in a number of different hues. Of course orange, green, purple, but you might also find something exciting with reds, teals or deep blues. Maybe even pink?