The coloring page features Spectra Wondergeist, an iconic Monster High character. She has long, jet-black hair with streaks of vivid purple throughout. Her complexion is extremely pale and her eyes are as dark as coal. She is wearing a simple black dress that has a purple belt encircling her waist and tall black boots. Adding to her unique look, is a sheer black cape with a shimmery purple lining. Her cute pet is a black cat with bright purple eyes and a white paw.
To color other elements in the picture, I would use shades of gray and purple to capture a sense of both darkness and mystery, while leaving Spectra as the focal point by using more saturated colors. A combination of lavender, lilac, and midnight blues could be used to achieve this striking look. Accentuating certain features such as her cape, belt, eyes and pet with a little glitter could help bring the page to life.