Blue is a blue-colored crayon (also known as a wax pastel), shaded with various different shades of blue. Her eyes and eyebrows are black, so are her arms, her mouth, and legs. Her tip on her head is smooth/round.
In Time Wasters, Blue witnesses how Pink is fascinated about the colorization of Green's line art on a drawing. Eraser Wash storms in and announces her panic about Cap's disappearance. Pink thinks she knows the answer as she tells a whole story, but Blue instead acknowledges how Cap was giggling about climbing the Summit of the Bookshelf. Eraser Wash thanks the crayons and hurries to the bookshelf.
Not much is shown of Blue, but by giving right information to Eraser Wash, she seems pretty intelligent, but is unfortunately a very quiet crayon.
- Green: Green is a friend of Blue's.
- Pink: Pink and Blue are friends.
- Eraser Wash: Blue once helped Eraser Wash find Cap.
- Blue seems to be a bit shy.