The short begins with Mabel giving a not very accurate history lesson about colors. She states that the world was black and white until a wizard named "Crayondalf the Fabulous" gave it color and ended the Depression. Mabel then surveys Pacifica, (Her favorite is hot pink) Grenda (beige), Dipper (Wendy), Soos (too many), Wendy (flannel), Candy (some weird thing), and even Gompers (burgondy) on their favorite colors. When she gets to Stan, she discovers that Stan has never seen a rainbow. Mabel consults Candy, Grenda, and Dipper on how to show Stan a rainbow. Grenda says that when she drinks expired milk, she sees rainbows, and then drinks a carton of milk. Candy comes up with the idea to reflect a rainbow from the waterfall to the Mystery Shack window. Candy and Dipper hold up a giant mirror and reflect a rainbow into Stan's office window, which is unfortunately very powerful and hurts Stan's eyes, as well as setting fire to a few things in his office. The short ends with Dipper and Soos wrapping bandages around Stan's face and Mabel saying that next week's episode will be about apologizing to your great uncle.
- Kristen Schaal as Mabel Pines
- Jason Ritter as Dipper Pines
- Alex Hirsch as Soos and Stan Pines
- Niki Yang as Candy Chiu
- Carl Faruolo as Grenda
- Jackie Buscarino as Pacifica Northwest
- Linda Cardellini as Wendy Corduroy
- According to Mabel's survey, everyone's favorite colors is as follows:
- Stan doesn't have a favorite color and he had never seen a rainbow until the end of this short.
- It is lightly implied that Mabel is a fan of Pink Floyd. The sweater she's wearing has the same triangular prism symbol found on the cover on Pink Floyd's 1973 album "The Dark Side of the Moon".
- Grenda falls asleep and sees rainbows every time she drinks expired milk.
- Mabel's seen wearing the strawberry sweater from "Headhunters."
- She's also seen wearing the swimsuit she wore in "The Deep End."
- The picture that Candy holds up in the "whats your favorite color" segment is an autostereogram, which means when looked at a certain way will reveal a 3D scene using a two-dimensional image. This one doesn't appear to contain anything though.
- Mabel refers to the plan which will send a rainbow into Stan's office as the "Roy-G-Biv-A-Tron." Roy G. Biv is an acronym for the sequence of hues commonly described as making up a rainbow.
- "Mabel's Guide to Colors" was released on Disney Channel's official YouTube channel an hour before it premiered on the east coast. It was posted along with the rest of Mabel's Guide to Life shorts.
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