The star of Blue's Clues, Blue, is a girl puppy who communicates to Steve and Joe through barks, which they understand. Every episode she initiates a game of Blue's Clues in which she leaves three paw print clues for Steve or Joe and the viewer to find in order to a question.
Magenta is Blue's best friend from school. She looks exactly like Blue except she is magenta with magenta-colored spots. Magenta likes photography and making macaroni picture frames.
Mailbox lives at the foot of the pathway in front of Blue's house. He sits on a post, and gets the mail, delivering it when it comes. When he delivers the mail, he comes in through the living room window to the right of the Thinking Chair, on an "extendo" arm. Mailbox is a boy, with a thick Brooklyn accent. He fancies himself quite the comedian.
Periwinkle is the boy cat who moves in next door to Blue. Unlike Blue, Periwinkle does talk, and among his favorite hobbies is being mischievous and practicing magic.