What is a 1 color perfector on a printing press?

A "1 color perfector" is not something that is "ON a printing press. A Perfector is a type of printing press that prints both sides of the sheet simultaneously. It can print either, 1, 2, 3, 4 or more colors dependent upon the amount of Units or Towers placed in sequence. A Unit or Tower is a section of the press that creates a single color using separate inking system, dampening system, plate, blanket and impression cylinders.