There was a large population of wild dogs out in the snowy wilderness of Siberian Russia. The dogs overproduced in their population, meaning that not all of their babies are able to survive to maturity.
The three very different kinds of dogs went out into the winter snow to attempt to find more resources to give their children and keep them alive. Things would not go as planned unfortunately, thanks to the devil.
Because the white variation for the dog species was able to blend in, it did not get seen by the devil and was safe. The other dog variations were not quite as lucky, however.
The white variant of the dog population, thanks to it's color and being able to blend in with the snow, made it back to it's children safely.
Thanks to the selection process, this better adapted variant of the dog species that is able to blend in is able to survive and reproduce more than the other variants.
The children inherit their mother's characteristic of white fur through the process of adaption, and are given a higher chance of surviving. The babies grow up and live happily for the rest of their lives, devil free.