Color matters in The Sixth Sense, and red is the most famous example for a reason. Shyamalan uses it sparingly enough that it registers whenever it appears, but not so loudly that it starts feeling like a gimmick.
Red as signal
Throughout the film, red tends to show up around moments of emotional rupture, supernatural intrusion, or transition between the ordinary world and something more spiritually charged. It is not a mechanical code that explains every scene, but it is a recurring visual signal the film uses with unusual care.
Muted surroundings
The red stands out because so much of the rest of the movie is restrained. The Sixth Sense often lives in softer neutrals, cooler tones, and subdued domestic spaces. When red enters that quieter palette, it feels disruptive on purpose.
Feeling before explanation
One of the smartest things Shyamalan does is use color in a way viewers can feel even before they consciously track it. The movie does not stop to explain its own visual logic. It trusts the audience to absorb it. That trust helps explain why the film remains so effective on rewatch.
In other words, the red is not there just to be spotted. It is there to make the whole movie feel slightly more haunted whenever the boundary between worlds grows thin.
The restraint matters too. A movie like this could have turned the red motif into an obvious trick, with giant neon arrows pointing at every meaningful object. Shyamalan does the opposite. He lets the color show up, register, and drift back out of sight. That is a big part of why viewers keep noticing it more on rewatch than on first glance.