Rainbow Soup takes place in a richly detailed world of wonder, imagination, and fantasy. It manifests the power of love, friendship, and positive thinking through Chantelle - caring and devoted granddaughter of Popper - who treks through the Rainbow to find the legendary pot of gold to bring home to her grandfather. During her travels in the Rainbow, Chantelle encounters a host of memorable characters, including Rainbow Fairies, the Guardian of Light, the Prince of Special Effects, and various personifications of the elements of weather: the Four Mistrals (winds); the Cloud Tinker and his sister, Mother Rain; cloud Whispies; and the Storm Warrior. And she discovers that Rainbow soup provides the inspiration for, and medium in which to create, sunrises, sunsets, rainbows, and all forms of amazing sky art.

Chantelle also has to face the hostile challenges of Neanderyl and the Black Brigade, who steal from the pot of rainbow soup to feed their monster storm, the Tempest. Ultimately, the Tempest descends on Chantelle's home and threatens to destroy it, then holds two of her most treasured Rainbow friends hostage. In her attempt to save all that she loves, and reunite with her grandfather, Chantelle comes to understand the bonds of family and friendship are the true source of personal wealth.