To the best of my knowledge, the original Calicos were the result of a really bad problem where (it looked like) the immune system was attacking the pigment. Basically bad news.
Later a guy who is now long gone from the corn scene (and from everything I hear, this is a good thing) was advertising a "new" line of them or something, but nobody has ever seen any of that come to fruition... that I know of anyway.
Flourescent orange corns are a
SerpenCo line of amelanistics. See the "available" list and click on that morph for the lowdown on it.
Snow is the combination of Amelanism and Anerythrism both being expressed in the same cornsnake.
A Blizzard corn is Amel and Charcoal. These tend to show less pattern than snows, and AFAIK don't have so much of the pinks and other odd colors that many snows develop as adults.
Pearls are still a mystery. Nobody has nailed down what exactly they are...