One of the most dramatic scenes of the movie sees the protagonist, Amy Elliott Dunne (Rosamund Pike), cutting her hair and dying it dark blonde. She uses a L’Oreal hairdye, which I first identified as being part of the Superior Preference line. The only odd detail is the cap of the color gel: it should be gold, but in the movie it’s black.
Later in the movie, Desi Collings (Neil Patrick Harris) takes Amy to his lake house. He buys some toiletries for her, including a box of L’Oreal Superior Preference hair dye in Natural Blonde. Ta-dah! My id was correct. The fact that the same hairdye appears twice makes sense to me. “I just want you to be you again,” he repeats, and going back to blonde is definitely a step in that direction.