In The Matrix, what color is the cat that creates a déjà vu effect? The answer is black.
Neo notices a black cat pass through a doorway, followed immediately by an almost identical black cat. Trinity explains that déjà vu is a glitch caused when the Matrix changes something in its programming. In this scene, the apparent repetition signals that the system has altered the environment around the rebels.
The cat is not the cause of the change; it is the visual clue that lets Neo and the others recognize a system anomaly. The group soon discovers that the exit route has been tampered with and that they are trapped inside the building. This is why the moment matters despite its ordinary appearance.
A common mix-up is remembering only that the cat appears twice and overlooking its color. The white rabbit is a separate visual motif from earlier in the film: Neo follows a tattoo of one before meeting Trinity. The déjà vu cat is distinctly black.