Irish Setters with no red hairs.
Just as adults often go for the unusual, children very very often will ignore the normal puppies in a litter and only play with the odd colored puppy or kitten.
This is because children have a very hard time learning to distinguish between one puppy and another. Children often look at patched colored puppies and just see them as a bunch of patched colored puppies - they don't remember the shapes of the patches.
Even if you say "The puppy's name a pupy after his markings, the child wont recognise the puppy when they see the other side of the puppy. And most children lack the patience to stand there and wait and look - they just want to run up and grab a puppy.
It is the same with kittens. I knew people who bred purebred cats, the children got use to there always being kittens around - but then, one of the kittens was born an off color (for that breed of cat) and the kids adored it. Why? Because they could recognise it from the other kittens.
The reverse happens in laboratories. The company deliberately uses mice, rats, guinea pigs, and rabbits that are all the same color albino. Because if the animals were distinctive then the experimenters would identify with the animals as individuals and the experimenters would feel sorry for a favored animal.
I knew of a litter of kittens where all the kittens were the same color but one. The children played most with the one different kitten - the other kittens had names - but which name went to which kitten? Only the odd colored kitten could be properly labeled.
The boy in this family was cruel and he would pick on the kittens who look alike. Worse, in my opinion is when you find a child who seeks out the unique puppy or kitten t pick on.
The unique or identifiable animal is one that the child can have a personal bond with. The other animals, like flocks of purebred chickens, or kennels of many purebred dogs and cats, are too similar for a child (and often adults) to tell apart.
Seeking out, and favoring, the distinctive animal is normal. Being more able to harm an animal when they all look alike is more normal. But hurting, especially seeking out to hurt, an identifiable animal is not a good moral sign.
Why some people want to breed dogs and cats to get groups where they all look so such alike, I don't know.