Gatsby does indeed wear a pink suit, and it assumes significance in the novel when taken in context. Tom cannot believe that Gatsby ever attended such an old and prestigious university as Oxford because Gatsby clearly does not belong to the upper class.
Gatsby's pink suit makes a statement to Tom; it says that Gatsby flaunts his wealth--which is "new" money. He does not dress in the tasteful, conservative, understated style adopted by those who have inherited their family fortunes, money that often has been handed down through several generations. One of the unwritten rules of Tom Buchanan's social class is that those with a great deal of money do not display it in a vulgar manner. To do so would be quite gauche. Gatsby in his pink suit shows clearly that he does not know the rules.
Everything Gatsby owns, from his pink suit to his colossal, faux-European mansion and "circus wagon" touring car, show his lack of upper-class taste and refinement. No matter how much money he accumulates, Gatsby will never be the kind of man who "belongs" at Oxford.
In The Great Gatsby, the reference to Gatsby wearing a pink suit appears in Chapter Seven when Tom, Nick, and Jordan are discussing the possibility that Gatsby attended Oxford University:
“An Oxford man!” He was incredulous. “Like hell he is! He wears a pink suit.”
By using these words, Tom is arguing that Gatsby could not have attended Oxford because he does not belong to the correct social class. Gatsby is brash (as evident by his wearing a pink suit), materialistic, and flaunts his wealth at lavish parties. The pink suit therefore symbolizes Gatsby's status as an outsider. Gatsby does not belong to the old-money world of Tom and Daisy, but his enormous wealth does set him above the typical American. As a result, Gatsby treads his path alone as he carries out his mission to be reunited with his long-lost love, Daisy. As such, his pink suit demonstrates just how isolated and different he really is.
I noticed that pink represents a surreal feeling of romance early on in the book. Pink and gold are used a lot to describe when Daisy and Gatsby are together