Roman Horsehair Crests

[TraderTrey9785]

Okay, so here is a question that has popped into my mind quite often lately and I can't seem to find an answer. What was the color of the crests worn atop Roman helmets? Usually they are depicted as being red, however I recently read that most were actually yellow. Obviously some are portrayed as black also. Does anyone know if they were one specific color, or a variety? Did a different color denote rank or seniority in any way? Any websites, book references, or comments would be great!

Thanks!