This spooky scene features a mysterious witch, stirring a cauldron surrounded by an eerie green light. Resting atop the edge of the cauldron is a lazy black cat, and a rat scurries around the witch's feet. On her shoulders, a large raven perches menacingly. Her face is long and hooked, with sinister black eyes, and her clothing is tattered and dark. A large black cape hangs from her shoulders, lending the scene a gothic feel. Behind the witch, deep shadows hint at secrets and secrets yet untold.
For this scene, I'd recommend using a blend of deep shades of green, grey and black. A lighter green will work for the eerie green light created by the cauldron, while darker greens will provide the shadows for the background. The witch's clothing should be painted in dark shades of grey and black, as should her cape and her pet rat and raven. Finally, her cat could be painted with a light grey or white.