Red/orange colored farlowella catfish?

[FF_Member146894]

a little while ago, I bought two farlowella catfish from my local fish store (which were simply labeled "farlowella catfish") and I've noticed that one is much more red whereas the other is a darker brown.
i've never kept these in the past, and when I search for "red farlowella" or something along those lines I get images of something completely different.
is this a normal coloration difference between males and females, a species difference, or something that I should be more concerned about? (I would post this in the emergencies section, but it isn't necessarily an emergency.)

realzalio

and here are some water parameters:
pH - 7.0 to 7.2
ammonia and nitrites - 0 ppm
nitrates - below 20 ppm
GH - 8 dGH
(last time I tested - 2 days ago)

 

[Byron]

Identification of species in the genus Farlowella is not easy, and there are currently 27 described species, of which only two or maybe three were regularly being exported. What is imported as F. acus has often actually been F. vitatta, and the other imported species is F. gracilis. You can see photos of most of the species on Planet Catfish, here:
Species Quick Find (planetcatfish.com)

A more red colouration is sometimes due to certain items in a fish's diet, but I am not suggesting that is the case here.

 

[FF_Member146894]

Identification of species in the genus Farlowella is not easy, and there are currently 27 described species

that's what I assumed, but I wanted to be sure.
thanks for reassuring me!