On the other hand, if it isn't expressly winter related, it could be that her "white coat" reacted with a more complete expression of the barring protein (resulting in more pigment supression) and when she had her "black coat" she had lesser expression.

it could even be diet related.. if she didnt have the correct amino acids for the specific color suppressing protein caused by the barring gene she could have ended up black because she couldn't produce as much!
Normally diet has little to no effect on color. Barring could be an exception though. The barring gene is actually a gene that was meant to produce a UV resistant protien periodically through the coat, which then mutated and lost some vital info and became a "nonsense" gene, but still caused a protien to be produced throughout the feather layer. That protien is now close enough in size ect to the normal "stop" code for melanin/pigment that it started messing with the pigmentation, mostly with melanin. Since the resulting color is dependent upon a continuously produced protien instead of the genetic code is is subject to outside influence.... which is honestly very cool.


Maybe one of the 4 mutations responsible has a stabilizing effect normally, making the protien amounts limited and evenly produced through the year, or it could even be a 5th mutation on the gene responsible for that!

I would probably be looking up the amino acids necessary for that protien and super charging her diet (within safety) to see if i could get her to get lighter, or dropping those less necessary ones to a lower amount and seeing if she got darker! It would probably only work during a molt, but would be so fun to test!!!
Of course, most of this is alot of maybes based off of loose genetics we as a species dont really know that much about.... so you know, grain of salt.
