After one of Ernest the wizard-lizard's spells goes awry, draining color from Princess Prism and her domain, the unicorn princesses call on the human girl Cressida to help Prism locate the Valley of Light's missing rainbow so she regain her magic and repaint the land and creatures.

Princess Breeze invites her human friend, Cressida, to attend the Blast, a festival featuring kite flying, but the wizard-lizard, Ernest, has blundered again and now giant bats sleep on the kites.

"Princess Bloom has been hard at work planning her birthday ball in the Magic Garden. When her human friend Cressida arrives to help with the finishing touches, they find a flock of quails destroying all the food and decorations. Bloom is heartbroken! Can Cressida find a way to save the garden ball? One thing is certain - she'll need the magic of all the Unicorn Princesses to do it! Cressida's visits to the Rainbow Realm lead to many exciting adventures...