Marie's favorite color is obviously purple. I always thought it was to symbolize her need for control over the aspects of her life and her kleptomania is a manifestation of this. Hank is always dressed or surrounded by golden, honey like colors because he's a warm spirit. Skylar has blue tones that can be soft yet cold in appearance, much like her personality. That's all I have so far lol. I've been noticing it since the second season, good to know I wasn't far off by paying attention to the colors.