Q. Why are some breeds at dog shows divided by color (Cocker Spaniel) or coat length (Collie, Dachshund) with two or more representatives in the Group judging, but other breeds (Chinese Crested, Chow Chow) are not?
A. It is purely arbitrary. One very obvious example of that would be the English Toy Spaniel which is divided into two varieties, the parti-colors and the whole colors (or solid colors). The Cavalier King Charles Spaniel comes in the same four colors yet only one representative is chosen Best of Breed and appears in the judging of the Toy Group.
Originally, splitting up colors, as in Cocker Spaniels, was done to give some of the less popular varieties a boost or a crutch. This isn’t needed today. For new breeds working toward American Kennel Club recognition, the club discourages splitting of varieties on the basis of color or coat length.
Many breeds have their Open classes divided by color (e.g. Great Dane, Doberman Pinscher, Pomeranian) or coat length (Chow, Saluki) at shows although only one dog is chosen Best of Breed.