Each night, when Ben falls asleep, his Crayons’ magical Crayon Box transports them to Colour City. But when Yellow is accidentally left behind, she awakens two Unfinished Drawings, who follow Yellow to Colour City to claim the enchanted Rainbow Waterfall and all of its colour for themselves.

Now, it’s up to Yellow and her pals, Blue, Green, Red, and the twins, Black and White, to stop Colour City from fading and all the crayons from disappearing.