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Genetics of color mutations in the snake, Elaphe obsoleta
H. Bernard Bechtel, Elizabeth Bechtel
Journal of Heredity, Volume 76, Issue 1, 1 January 1985, Pages 7–11, https://doi.org/10.1093/oxfordjournals.jhered.a110026

https://owlcation.com/stem/Stunning-Albino-Animals

I like leucism, too. The above may help.

I am not surprised that you are confused. As far as I know, there are probably a number of conditions that have been lumped together under the term. Some definitely are genetic, such as the leucistic rat snakes in the Bechtels' paper. Other conditions may not be. And there it is no reason that a given type of leucism cannot be both genetic and a skin defect where there is no migration of melanocytes in the skin during embryogenesis.

I must shut down now.