Yes, you are correct. There are 5 livery fields available for each aircraft in the Aircraft Manager page and this allows you to add multiple different liveries for each aircraft.
So for example, with the KLM E90 you could have the current KLM livery in Livery 1, the old KLM livery in Livery 2, and a special livery in Livery 3, and the FS Traffic module will pick one of these liveries at random when generating the aircraft in the simulator.
Mark - Just Flight