This character dresses like a Rummage Sale Reject, and they're fine with that.
They will wear plaid and stripes together. They'll wear white after labor day. They'll wear neon green with orange. And the worst part of it is... they do it intentionally. These are the characters who really don't care if they have a Limited Wardrobe or an Unlimited Wardrobe, they'll dress like a Rummage Sale Reject either way. Please note, this is when their lack of fashion sense is noted In-Universe. This is not when the fandom or the viewers disagree with the character's fashion choice. There are two types of this.
Oblivious To FashionThe character is completely oblivious to the rules of fashion, and could not dress themselves without the assistance of a patient fashionista, a tailor, and a doorstopper of a "How To" guide.
Ignores FashionThis character does know the rules of fashion, but intentionally ignores it all, either to spite the status quo as a form of rebellion, or as a form of asserting their individuality. Will probably involve Impossibly Tacky Clothes. See also, Tacky Tuxedo. Examples: