As I told in another context, when males are absent dominant females could appear similar to subdominant males and exhibit certain colour features that they don’t show normally (even in the caudal, dorsal and anal fins). I remember to have seen this very clearly in a “widow” of a deceased male P. tweediei. The extreme is P. ornaticauda, where females in normal courtship appear temporarily just like males, even with the red flame in the caudal fin. I remember the first time when I saw this: I thought that there were two males in the tank, but I remembered to have put a pair into it. It was a pair.
But it’s a completely different thing with parvulus. The females never dress like males. Only in the absence of males some could show that bluish fine borderline of the anal and dorsal fin. It’s obviously a matter of different location forms: the one do it, the other not. Since P. patvulus is probably the Paro with the most comprehensive occurrence, these differentiations are very likely to have occurred in the evolution of this species generating variants that still belong to the same species, however.