Ok, this may seem a little bit absurd but studying Balto's colors it seems almost impossible to me that Balto's mother was a pure white wolf. Now here's my reasoning: first of all, if you look at a picture of Balto, his colors are a very deep brown that (to me) don't seem to hint that he had an all white parent. You can see for yourself:

Second point is that Balto mentions her to be as white as snow but he also says that he was separated from her when he was really young. Could it be possible that he was so young back then that the only features he remembers from his mother are just a white underbody, paws and face? It could be possible that his mother indeed had a brown back but being so young Balto never had a chance to develop in sight and size to see those features?

Now I know what you're probably thinking right now: 'But Aniu appears at the end of the film and Balto calls her his mother and she is white!' Well, I personally (and you can hate me for this if you want) don't believe that last part of the movie. I don't think a wolf can just appear out of nowhere and dissappear again, do you? Ye, it's just a made up story but so many people have taken the Balto movies seriously that I don't feel awkward pointing this out. I'm not asking you to agree with me so if i ever post my version of Balto's parents, don't flip out if Balto's mother will be partly brown.

Thanks for reading!