I think you misunderstood my post. It's not a matter of perception at all.Once again, a matter of perception. The darker Coral Snake, once you see it, side by side, to a King snake, there's almost no comparison.
The "red next to black/red and black friend of Jack" rule does not hold outside of North America.
Outside of North America there are Coral Snakes which have adjacent red and black bands. Here is an example that ranges from upper South America into Central America. Note that in the picture it has adjacent red and black bands but it is still a Coral Snake and still potentially deadly.
http://reptile-database.reptarium.cz/species?genus=Micrurus&species=dissoleucus
Outside of North America are Coral Snakes which have no yellow on them at all. Here is an example of a Coral Snake from Central America that has ONLY red and black markings--nothing at all remotely yellow or light-colored. And yet it is a Coral Snake.
https://www.inaturalist.org/observations/40294764
The little poem about distinguishing Coral Snakes from non-venomous snakes by whether or not there is yellow or black adjacent to red bands should ONLY be relied upon in North America. Once you get down into Central America--even as far north as some parts of Mexico--the rule does not hold.
It's a great rule for use in North America. But it could be fatal to assume that it works everywhere.