Used means this PASGT helmet has been used but is still in good condition, it has some wear and possibly remnants of tape on the shell. It has absolutely no damage or anything that would affect the functionality or integrity of the helmet.
The PASGT helmet is the last generation of ballistic helmet that was used by the military. This helmet can be bought as just the helmet shell, the helmet with the new head band, or the helmet, new head band and pre-owned BDU helmet cover.
The different colors are just painted PASGT helmets.