The first Coral was a random occurrence. It wasn't bred for, it just happened. Then efforts were made to breed for more, and found out it's sorta sporadic, and unpredictable. You
can't count on half or even ¼ of the litter obtaining the trait, although it's certainly possible for it to happen. You just can't predict the outcome, or state that a certain percent of the litter will obtain the trait. It just don't work like that.
I talked with Kahl for over 2 hours about this trait back in '99 at the Orlando show (now known as Daytona Expo) trying to understand it, because I was picking out one of the litter mates from the litter that threw the first Coral. His story was simple, he didn't know where it came from, it just happened.
As time went on, and more breeding trials were done, it was found out that the coral trait can effect any one of the litter, Albino or not. It was found out that even a mild expression Coral can throw extreme examples of the trait, and extreme examples can throw mild examples of the trait. And that the percentage of the litter that got the trait was very inconsistent and unpredictable.
That comes straight from Kahls mouth to me during our conversations on the subject over the years. I like Corals, might even say I have a thing for them, so I've tried to follow them as much as I can. Problem is, once the first Albino Pastel was born, and it resembled a Coral Albino, they all became Corals after that. And worse yet, any high colored Albino gets tagged with Coral as well, making it very difficult to follow the lines that had true Corals, but no pastel blood in their lines.
All these bright colored "corals" you see these days, are probably just Pastel Albinos, mislabeled as Corals. Even Pete went this route the past few years, perpetuating the problem by calling them Corals when he used a Pastel to achieve the color.
What I've observed trying to mess with and learn more about the trait, is that there are definitely visual differences between the real Corals, and Pastel Albinos. The traits may very well work in the same manner, being sorta polygenic in nature, but Pastels have a predictability that Corals will never have. Corals do not flood the whole body with Color , but more of a marbled look, AND the color is more pink, not red or orange. That's why it was called Coral. Additionally, very few of them make it known at birth they are Coral, but rather the trait tends to come out later in life. I think I've produced 2 that made it obvious at birth, and a few more that I suspected were Coral, that never really took off with the trait, some are still growing, so I gotta wait on them. On the flip side, I sold a few "normal" Albinos that exploded with the trait as they approached the 2-3 yr old mark.
Anyway, long story short, I agree with Harald. The term has been grossly misused, and as a result is pretty useless except as a marketing term that every Tom, Dick and Harry is using to get an extra dollar for the animal. It's gone from a very interesting trait, to a big old headache trying to follow and work with them to further understand the trait, and how it passes on. I've all but given up on this subject anymore. I got the genes in my bloodlines, and I'll continue to play with them, but the seriousness I once had about it is pretty much gone, due to the mess that's been created surrounding the trait over the years, and the misuse of the term.
That's my story anyway, as best as I can remember. I'm sure somebody will come and disagree with it though.

That's part of the problem too. A lot of, "well, so and so said" going on.