Rainbow Brite and the Star Stealer (1985)

Rainbow Brite and her magical horse, Starlite, must stop an evil princess and her underlings from taking over the planet Spectra. When she and a new acquaintance named Krys meet Orin, he tries to make them get along and work together to stop the princess. Orin tells them that they can only destroy her by combining their own powers against her. Getting in the way of their mission is the sinister Murky Dismal and his bumbling assistant, Lurky, who, as usual, are lavishing in the new gloom created by the darkening of Spectra, as well as trying to steal Rainbow's magical color belt.