Rainbow was a first generation Spaceknight whose main power was emotional manipulation.
Little is known about Rainbow. She was one of the first generation Spaceknights that had returned to Galador prior to the return of Rom. Rom was able to free her upon his return to Galador. Rainbow used her Emotion Manipulating Light powers to stop their attackers, the Angels, without harming them. She and the other freed Spacekinghts helped defeat Mentus and Terminator.
Not long after they were attacked by Galactus, and his Herald Terrax.
Rainbow engaged Terrax in battle using her Rainbow light power to make him feel compassion for their plight. But he resisted easily and defeated her. The Spaceknights rallied and were also able to subsequently prevent their home-world from being devoured by Galactus.
She is next seen on the asteroid with the other Spaceknights awaiting a plan of action, after ROM leads Galactus to the Black Nebula.