Man, those are all great questions, and I am not real sure at all about having the answers to all those either to be honest. Sort of goes back to what I said about "the more you seem to find out, the less you actually "know" many times..LOL!
That Martir agalma is sort of tough to tell exactly from the pic, plus it still has to shed too, so it could look a bit lighter now than what it might look like later on.
Xanthophores can affect the way reds AND yellows look to us, so alot of it still puzzles the hell out of me. It seems that if reds and yellows are BOTH absent from what would normally be a tricolored animal, to me that would probably a very accurate example of "axanthism" being expressed. A snake that doesn't have any yellow to it's normal color scheme, but only red,and black/gray then the red is removed, this seems to fit the term "anerythristic" very well. But here we have the word "seems" again..LOL!
It does "seem" to me that the bluish hued snakes(like the NE axanthics with dark eyes would be accurately called "axanthics", but the reds are normally displayed in tons of floridana as you know too, so this is not real absolute at all to me either. Then the so-called anerythristic morph has still got me puzzled there too. Could these both be just a slightly different form of the same exact thing??. I mean neither one has yellows OR reds either..LOL!. I have trouble thinking an animal is anery when when there might not be any red in the equation whatsoever. Even the very red brooks I produce as babies had a sibling female that had absolutely ZERO RED on her entire body as a hatchling,..not even a portion of one single scale!, but she did have the fairly typical yellowish/green crossbars and speckling. So as we both know there are many floridana that don't necessarily have to have any reds in their coloration. So what if THOSE specific animals started a line that didn't have any yellow?, what would they REALLY BE??.
Man, alot of the terms have me going WTF big-time in the hobby!..LOL!. Like the so-called "anerythristic splendida for example. Okay, they don't have any red to them whatsoever at any stage of their lives, so I can very safely assume that they cannot be anerythristic, because the very prefix of the word anerythristic begins with..."AN", and that means lack of, or NONE, and the rest of the word.."erythristic" pertains to red pigment. Put them together, and it means "NO RED", simple as that. The term "anerythristic" splendida makes zero sense, as it only consists of black/yellows/whites, NO red, so they HAVE to be AXANTHIC(no yellows/creams)to me, just black and white.
Even a hybrid example as you mentioned of an axanthic brooks x tricolor, then back-bred, then if any animals had any yellows/creams at all but no red, it would seem to fit the term "anerythristic" more accurately if it played-out that way. But if any animals had no reds OR yellows, I would again think that "axanthic" would be a better term.
But what is really weird is, how does a freakin so-called "anerythristic" Honduran fit into what the heck I just pointed out??..LOL! I mean, they have neither red(debatable with some)but no yellow either, so if they are really "hypoerythristic"(extremely reduced red), then WTF about them not having yellow in the middle ring of the triad??..ooooh my head is truly starting to hurt right about now, holy smokes man!!..LOL!!
I am guessing the bluish brooks that are called "axanthic" could very well be JUST THAT, but couldn't the duller, less contrasty ones we call anery's be just another type of axanthism too??....think about it, I do all the time, and it leaves me puzzled as all heck every single time..LOL!
I don't have Bechtel's book, but I would really like to see what type of milksnake he was referring to though.
I don't honestly think I answered any of your questions at all really, it just made me think real hard about the terms and what "might" be going on genetically, but me typing all this guess-work of mine makes me just as unsure as I was when I started the post in the first place.
Yeah Rainer, this stuff is really way more complicated than we will EVER know in my opinion. Sometimes I almost wish I knew absolutely nothing about snakes, it would be so much easier on my head..LOL!
So after all this head straining crapola I typed here, I am really probably right back to the original place I first pointed out earlier, and might even know far less now than before I started typing any of this...LOL! I am afraid to even proof-read any of this because it probably makes little sense, so I won't..LOL!, I just rolled with some thoughts as I went for whatever it is worth..HAHAAA!!
Okay Rainer!, thanks for the headache bro!!..LMAO!! 

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"a snake in the grass is a GOOD thing" 
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