There were three different Maquis rank pins, although with minor oddities regarding the amount of black on them.
All the insignificant background Maquis characters and one-offs wore the pin with a single black slash. If this corresponded to the single black pip of regular Starfleet personnel, it would signify a noncom - but it was also the pin worn by, say, Ensign Seska.
We could always argue that some of the diagonals were "in fact" bright brass, which would indeed make them nicely match the regular Ensign pip. Our eyes or TV sets just "failed to reveal this".
Similarly, after her promotion to Lieutenant (junior grade) in "Parallax", B'elanna Torres wore a pin with two slashes. Sometimes this pin had one of the slashes colored black, which would correctly match the standard Starfleet usage. Sometimes both slashes appeared bright, though, and sometimes both appeared black. We could again argue that our eyes were playing tricks on us, and that the pin always correctly matched Torres' rank. Thus, we could also argue that she originally was promoted to full Lieutenant (with two bright slashes), and then demoted as the result of her "Prime Factors" mutiny to the junior rank which she rather consistently carries from there on (with the one dark slash).
The third pin, with three slashes, was only worn by Chakotay. One of the slashes was always black, correctly indicating Lieutenant Commander rank (even though Chakotay was never formally addressed by this full rank, the shorthand "Commander" being used instead).