The Rainbow King is a male character who is the ruler of the Rainbow Kingdom. He has a cousin who is over 1 million years old named Glummy Glooma. It's unclear if Rainbow King is connected to Glummy's uncle Grump.
It's unclear whether he has any relation to the other monarchs, Day Queen and the Night Queen, sisters who are in control of the sun and moon.
The Rainbow King is elegant and cares for every citizen of the Rainbow Kingdom. He is kind, sympathetic, and humble. When in exclamation, he uses unique phrases such as "flabbergasting fuschia". Though he possesses a wealth of knowledge, he shares his wisdom in riddles adding fun complexity to True’s adventures. He will do anything to help True on her journey but he knows that “true” success is achieved when True solves problems all on her own.
The Rainbow King is small in size and white in color. He has signature red, yellow, and blue spheres on his head, on the left, top, and right sides, respectively. He wears a red cape and carries a golden scepter.
The Rainbow King and True appear to have a special friendship with each other, to where he even trusts her with "castle-sitting" in "Frookie Sitting". In "A Royal Stink", the Rainbow King recognized True as the honorary queen for the day.
He is known to use phrases relating to color for exclamation. These phrases include: