The roan guinea pig is a black colored guinea pig with white hairs mixed evenly throughout its body.
There are types of roan guinea pig where other colors have been incorporated due to breeding
To be classed as a roan guinea pig, it can have just a patch of coloring or be colored all over.
They are often confused with dalmatian guinea pigs.
A roan should never be allowed to breed with another roan as they can be born with deformities often known as lethal white syndrome.
The roan coloration is found on many animals and is defined as a mix of white and colored hairs which don’t fade due the animal growing in age.
Roan is a mutation which is often found on horses..
Acceptable color combinations for the white hairs include any of the self, agouti, or solid colors
The roaning effect is often heavier behind the shoulders, resulting in a lighter shade on the rear part of the body. (source)
It is said that roan guinea pigs cannot be allowed to mate with one another, as a high proportion of their offspring will be born with deformities internally and externally such as tiny eyes and teeth problems and will soon die. They are given the term ‘lethal guinea pigs’ (source)
An animal with one copy of the gene is totally healthy. They are the ones that have the white/colored mixed patches
Guinea pigs with two copies of the roan gene are the ‘lethal guinea pigs.’ They are always pure white with pink eyes. (source)
If you have a guinea pig with dark eyes and a white coat, it is not a lethal. It may however have hidden roan, ie the white roan hairs mixed through regular white coloring – which makes it impossible to tell. (source)
Because ‘hidden roan’ is tricky to dicifer, a lot of breeders recommend not breeding any two animals that have any white on them unless you know their parents didn’t have roan. (source)