Congrats on the fry! only 2 more years to go! :lol: Seriously though you should be out of the woods here pretty soon and then can't treat them like normal, very small, fish that don't grow

. I propose we change the name from A. Calvus to A. Peter Pannus, since they never growup.?
I have found all variants of Calvus to be quite complicated in the variety of coloring arrays that they display for one reason or aNOTHER
A couple theories I have gathered from studying my tanks over the years:
I have a White Calvus male who will go all black if there are more females present the aq than he would prefer. This same type coloring is displayed when excess subdominant males or excess subdominant females are present (i.e. when they get pushed up into the corner of the tank.
When females fight I have noticed the coloring you've described. Body goes white/gray, bars obscured but head, lips and pec fins go black. The black seems to be prominent right in the middle of the gill plate as well. My humble theory is that the to fighters are obscuring their faces as one whole rather than a surface facial area with visually discernable vital parts (Like eye balls!). I think it simply increases their chances of not becoming vitally injured in the face.
When breeding you'll notice that AWESOME, pretty coloration where the black is at it's finest, the pearls are glowing, the bars are defined, the head is green/yellow (depend on variant of course), and finnage is showing its defined white trim, and lastly that gorgeous blue lip gloss (The blue, In Zambians for instance, is more or less prominent depending on variant although all variants display blue lips). That is my only gripe against the beautiful "Black Pectoral Calvus", they are so black that the blue in the fins rarely shows, it does a bit in the ventrals still but nothing like a Zambian. Still the "BP" Calvus is my fav.
Going all black can mean many things imho, But I would say "all black" much of the time (Assuming Substrate is of neutral coloration as black sub can make them darker generally) equals either stress, or at least dissatisfaction. This is of course assuming they're displaying all black minus the blue. Add the blue and you've got mate rivalry or romance.
Black head and white body usually means something violent is about to go down. :thumb:
I haven't kept many males together to observe them fighting because once they're big 3"+ it's just not worth damaging or losing one since they're so pricy/take so long to grow so I haven't seen a lot of the male rivalry poses, or fighting colors though I assume they're pretty relative. Just can't recall for sure off hand.
That's cool that you've got those fry going. I told you the first batches always seem to fail no matter how careful you are. It's like all the sudden, magic and they start surviving for you. weird. I got like 12 from my first spawn ever and the next 25 and so on... Now for whatever reason I am able to keep 2/3rds of ever brood if I wish although I have very much slowed down my raising of Alto fry. Now I'm raising one brood from one variant each year. This year is WHite Calvus year!