I don't know..."gold" fur (which doesn't have a standard as far as I'm aware--I think you mean poor red) would show through later, especially if the mouse is pink eyed.
There are no "rare" colors of mice. Some are more common in some areas of the world and some aren't. The pearl, though, is pretty uncommon in both the US and the UK (the two main mouse fancying areas).
mousetress, that's not exactly right. Both are caused by e/e and/or Avy/* in the US. They're the same color caused by the same genes, just different extremes. The AFRMA actually has them standardized as fawn, gold, orange, and red, depending on the level of color.
That's not true, either. Environment (specifically neonatal environment) affects color distribution, density and pigmentation as well, in ways we don't fully understand. The genes are still 100% identical.
This is most easily seen in some strains of pied laboratory mice who are genetic clones of one another (i.e. 100% genetically identical on every count except for sex) and all look slightly different.
Haha! Put it at 99.9999% then, in other words as closely identical as scientifically possible. They have to be for the validity of experiments to be accepted, what with the control group and all. When inbred for hundreds of generations, the identical qualities at every locus is the result. Ask the Jax Laboratories (no relation) or any other evolutionary biologist familiar with the modern strains of animal models available to science. In many of the strains of mice they have on offer, the individuals are genetically identical, i.e. their genes are exactly the same.
This is just a roundabout way to support the assertion that two mice who are a/a e/e (for example) can have very different appearances while having the same genes at play.
Charles Darwin, more specifically his ideas, are intimately at play in any animal breeding program, by the way.