Peduncle is the end of the body where the tail attaches to.
For colorations, I don't know exactly what IBC wants for everything, someone from the IBC would have to answer that or you can join ;-) However, there are some things I do know. But Coloration is a much bigger topic since there are so many variations!
If you have a Butterfly, the color needs to be clean and separate from each other; no bleeding at all!
Ignoring form at the moment, here is a good butterfly. See how the blue and the white are completely separate? Over time, that will change but for this moment, this is good.
This one is a messy or bad Butterfly. See how the reddish is bleeding into the white and there are splotches of red in the white as well? The red is also not solid red, it's red and pink colored. This is actually a pink Salamander, but still not a great Salamander
Salamander is the next, it's similar to BF but the body color is different from the fins (whereas a Red Butterfly is red body, red fins with different colored band around the outside). The body color should bleed into the fin colors and then there is a solid fin color with a BF band around the outside, should still be clean band. So the most common Sally's are blue body with red head and red fins with a white band.
Here is a good Sally. See the red head (not necessary but common), the blue scales lay over top the red. The blue bleeds into the fins but a good chunk of the red is still showing. And a nice white band around all the fins
This guy, while nice, doesn't show as much red. I'm not sure if that's a technical fault in IBC shows, but for a good Salamander, you want to see more red or whatever color is it on them, than that
Though most Salamander's are that color up there, some also look like this:
His blue doesn't bleed much, but that's okay.
Here is a Red Copper Salamander
Salamander's were based off of Mustard Gases in the beginning. The creator wanted them also to be called Mustard Gas which would then just be a coloration of: body being different from the fins with a BF band around it. This is what the original MG's looked like:
AquaBid tends to screw up MG's the most. MG's HAVE to have yellow fins with some sort of band around the fins. Common ones are Blue body, yellow fins and either black or blue band. As far as IBC, again, I'm not sure which of these is acceptable and which isn't.
This is what you want to see on MG's. However, the band is incomplete on the anal fin, that's not good. The band should go all the way around the fins
Despite what he's being called, this is not a MG. Most of the "MG's" you see on AquaBid are like this. A blue fish with a yellow wash in the fins, that is not an MG
Neither is this boy, just because there is yellow in the fins does not make it automatically an MG
There is also Copper Gas now, again, not sure of the status of the IBC but I'd assume it's accepted by now since it's been a few years. But it's the same thing as MG but instead of blue, it's copper. Here was one of my old boys:
He had the black band, though it was small. His copper color bleeds a little
Black Copper Gas (where the body under color is black like this one, it becomes Black Copper instead of just Copper)
A nice fairly clean Copper Gas
And there is also a Purple Gas, same rules apply. This one isn't as good since the purple color bleeds
And then there are bicolors. A lot of fish mistaken for MG's are actually yellow blue bicolors. If there is no band around the outside of the fins, it is not an MG but now a bicolor. A bicolor should have a solid body color and solid fins, color should not bleed between fins and body.
This is an example of bleeding, see how there is blue in his dorsal fin and caudal? You don't want that there ideally. This is a messy coloring
Here is a good Bicolor! Teeny bit of bleed but not bad at all
Another decent bicolor
As far as what is good messy and what is bad messy, all coloration types I believe can be shown, you just may be marked off for not having the right colors. I'm not sure if there is a Variation class for colorations or anything.
If you want me to tell you about a specific coloration, I can do that for most of them. I don't know what is accepted as far as marbles go but I'm sure most are accepted.