Why does scout think she's being put into a pink penitentiary?

In To Kill a Mockingbird by Harper Lee, Scout thinks she is being put into a pink penitentiary because Aunt Alexander wants her to become a fine Southern lady, being feminine, wearing dresses, being interested in boys, and demonstrating fine manners. However Scout, being a tomboy, resists these views because she has much more of her fun outdoors and playing with Dill and Jem. This is ironic because most people wouldn't view a prison as pink, but would view it in dull colors, such as dirty gray and brown, but Scout, having such a dislike for femininity, including prissy colors like pink, imagines her prison in pink.