Why the ancient Roman helmets had feathers?

The plume was made of dyed horse hair. Hair was the preferred material because it lasted longer. The red was to intimidate the enemies with the color red which meant blood. The color red was also a sign that the men were soldiers of the emperor. But remember, the ordinary soldier did not have a plume on his helmet except if he were marching in a triumph. Plumes or distinguishing crests were only for officers. The centurion needed the wide crest so his men could more easily see him in battle