Bruce or Sheila.
Bluey or Red
Privilege
Guilt
Marshmallow
Oh, looks like I’m not the first to suggest that. In that case: Coconut.
Natal multimammate mice? How about something regionally appropriate?
Ifu (more-or-less ee-foo) is Zulu for cloud (the Zulu for white is mhlophe but I reckon that’ll be a lot harder for most people to pronounce. the -hl- is like Welsh -ll- )
The Swahili for white is nyeupe, again hard to pronounce, but for cloud it’s wingu.
And for the brown one, insundu (in-soon-doo) is literally the Zulu for “dark-brown beast”…
Minor nitpick… It’s Bronwyn.
There is a mythological Branwen ferch Llyr.
Lily.
If we’re talking soft and white I think Cotton would work well
I do like the name Ifu and reserve the right to steal it for future use
Ice cream.
How about, “Cracker”? 
Whitey Bulger.
Yeah, I typoed that, and didn’t catch it (it was late, and I was tired). Thank you!
Wow, I wasn’t expecting anyone to even know what the hell I was talking about, let alone to be familiar with the other term for 'em.
I rarely hear/read anyone use “multimammate” and wonder, is it regional? Are you in the U.S. if I may ask?
And for whoever asked for pics, here’s my lovely little lady, with one of her spotted cagemates. The other pic shows the more familiar coloration: a band or “saddle” of brown or reddish across their backs.
https://uploads.tapatalk-cdn.com/20190517/2a76b40609226d4dab3ae29542d09018.jpg
https://uploads.tapatalk-cdn.com/20190517/c134e343fd832d01a92c303dc8c08814.jpg
Or Walter.
In the late ‘60s, my mom (white woman) worked as a secretary for a black man. My parents got a pair of kittens, one black and one white. While mulling over names, Mom’s boss said the black one should be named Bib, “black is beautiful.” Then he said the white one should be named Cracker. And that is how my parents’ cats got their names. 
It’s more of a technical or descriptive term. In the part of their home region I’m familiar with, they’re just called “field mouse”. They’re awfully common as a wild species.
No, South Africa.
Lard
Hey, it’s white.
Edna Winter?
Pat Boone?
My first thought was Snowball, a reference to The Simpsons (where the “original” Snowball, based on a vision Bart had where he was ascending to heaven, had white fur).
The next “obvious” choice is Ghost, from Game of Thrones (in fact, the name is given in the first chapter of the first book of the series).