Black

The black is a very popular self variety and is one of the most frequently exhibited, along with the PEW and cream. A variety suitable for the beginner as well as the experienced fancier, blacks can be a lot harder to breed than novices might imagine. Any colour fault in a black, such as a tan vent, white hair or white toenail will stand out against the dark background rather than remain unnoticed. The only outcross advocated for a black is another black, so they tend to remain very inbred. Some people believe that this is the reason that a lot of breeders have been struggling to get their blacks to produce litters, and that any they do get are smaller than average.
Blacks are naturally smaller mice. It is not possible to get a black mouse with the required colour of the same size and type as a PEW and some allowance is made for this. Despite this breeders should never use weedy or weak specimens as breeding stock and must always be aware of the quality required of a show mouse.
Although an outcross may not be needed for colour in a black, it may be needed for health and vigour. In my experience exhibition blacks seem to be one of the weaker varieties health-wise and UK breeders often seem to have trouble getting them to breed consistently. By only breeding from disease-resistant mice and outcrossing if needed, the breeder should be able to keep on top of this.
Blacks are naturally smaller mice. It is not possible to get a black mouse with the required colour of the same size and type as a PEW and some allowance is made for this. Despite this breeders should never use weedy or weak specimens as breeding stock and must always be aware of the quality required of a show mouse.
Although an outcross may not be needed for colour in a black, it may be needed for health and vigour. In my experience exhibition blacks seem to be one of the weaker varieties health-wise and UK breeders often seem to have trouble getting them to breed consistently. By only breeding from disease-resistant mice and outcrossing if needed, the breeder should be able to keep on top of this.

A good black should be hardly visible – by which I mean that it should feel like you are looking into a black hole. The best black I have ever seen had this effect on me and I have never forgotten it. It was so deeply black that it was hard to see its features because it was so uniformly coloured. The breeder of this black also never benched blacks that were tinted with other colours – they were black through and through. I have seen blacks exhibited with casts of other colours, notably chocolate and occasionally silver/blue, and these mice were just lacking that pure blackness that would have made them winners. One fault in the poorer of these mice was the colouring of the inside of the ears, which was not jet black.
The most difficult fault to eliminate from a black is probably the tan vent, which needs a combination of careful selection of breeding stock and sometimes outcrossing to a different strain of blacks with less tan. The artificial colouring of mice is strictly prohibited by the NMC rules, and any person doing this to make their mouse blacker would be disqualified. However, the plucking of an odd white hair is not banned and some breeders will do this before a show.
The most difficult fault to eliminate from a black is probably the tan vent, which needs a combination of careful selection of breeding stock and sometimes outcrossing to a different strain of blacks with less tan. The artificial colouring of mice is strictly prohibited by the NMC rules, and any person doing this to make their mouse blacker would be disqualified. However, the plucking of an odd white hair is not banned and some breeders will do this before a show.

A fault discussed in Jones's Encyclopedia of Pet Mice is tan hairs on the throat. As a judge this is not something I can say I have seen very often, so perhaps the UK has moved on from this since the book was published in 1979. It would certainly be nice to think so!
Cooke advises breeders that "Up to about four weeks the coat colour may be disappointingly greyish in colour, but thereafter the coat will moult through until six or seven weeks when it should look like black velvet. Avoid specimens with coarse coats, chocolate coloured feet, ears or tails". Albert Jude elaborated on why breeders should avoid mice with coarse coats in The Fancy Mouse; "What is needed is a coat that is fine in texture, short, dense and close lying. An open coarse coat will not make for depth of colour".
Cooke advises breeders that "Up to about four weeks the coat colour may be disappointingly greyish in colour, but thereafter the coat will moult through until six or seven weeks when it should look like black velvet. Avoid specimens with coarse coats, chocolate coloured feet, ears or tails". Albert Jude elaborated on why breeders should avoid mice with coarse coats in The Fancy Mouse; "What is needed is a coat that is fine in texture, short, dense and close lying. An open coarse coat will not make for depth of colour".