Cavy Breeds

Short haired
The short coated cavy - often called the American or English - has consistently short, glossy hair without a part. This breed of cavy most resembles the Guinea pig's relatives and ancestors in the Cavia genus.
In shows, short-haired guinea pigs are shown by their color variety - self, dalmatian, himalayan, etc. This designation does not have 'American' or 'English' appended to it, but applies only to short-haired animals.

Abyssinian
The Abyssinian breed of Guinea pig is known for its short, rough coat that has cowlicked rosettes of hair. The derivation of the breed's name is unknown, but does not connotate an origin in the geographical region of Abyssinia (present day Ethiopia). The ideal Abyssinian has 10 rosettes, one on each shoulder, four across the back, one on each of the animal's hips, and two on the rump. Some judging bodies, such as the ANCC, consider shoulder rosettes optional but desired in show cavies. A harsh-textured coat that stands on end to form ridges is desired.

Peruvian
The Peruvian is the progenitor of all modern long haired breeds, being a Guinea pig with hair that grows long continuously all over its body, sometimes to an excess of 20 inches (approx. 50 centimeters). Accordingly, this ornate feature can make caring for this breed more difficult for both owners and breeders; most show Peruvians have their hair folded up in wraps to protect it and keep it clean. Long haired Guinea pigs have both a top and an undercoat, the latter of which will generally only grow to 6-7 inches (15-17 cm.)Though most Peruvians kept as pets are regularly trimmed for ease of keeping, those in show coat should have hair that fans out to make the animal's front and rear completely indistinguishable. The coat should be of an even length all over, and have a central part on the spine. Peruvians of show standard are required to have two rosettes on either side of the rump, which creates the desired height and density.

Silkie or Sheltie
A Silkie has long hair that flows back over its body and never forward over the face (as in the Peruvian). When viewed from above it forms a teardrop shape and should never have a central part. In contrast to the Peruvian, where the coat is desired to fall in an even curtain all around the body, the Sheltie is generally accepted to have a somewhat longer sweep of hair in the rear.

Rex
A Rex guinea pig has short, fuzzy hair that stands on end all over the body. The hair should be uniform all over, without rosettes and no more than 1⁄2 inch (1 1⁄4 cm) in length, preferably shorter. The Rex breed sometimes looks similar to the Teddy, but the two breeds are genetically distinct--breeding a Rex to a Teddy will not result in Rex or Teddies, but rather American cavies.

Teddy
A Teddy guinea pig has a very dense and fuzzy coat, with hairs that stand up. The fur typically grows to a moderate length and generally makes this breed resemble a soft toy more than any other. Another unique feature of the Teddies is the relatively long hair coating their bellies, in contrast to other breeds, whose bellies are nearly bare. Young Teddies sometimes look similar to the Rex, but the Rex's fur is shorter and usually much more bristled. There are two kinds of Teddy: The US Teddy and the CH Teddy, otherwise known as the Swiss Teddy. The two variations appear to be both genetically and visually different.

Texel
A Texel Guinea pig is like a Silkie, but with curls. Originating from England, it was officially recognized as a breed by the ACBA in 1998.The curls should ideally be tightly wound corkscrew curls and should cover the entire body, including the stomach. Unlike a Sheltie, a central part is allowed.

Relatively rare or emerging breeds

Alpaca
A curly coated Peruvian. Hair grows over face like a Peruvian. Most are first generation hybrids of Peruvians and other breeds.

Crested
The Crested is similar to the American, but has one rosette on the top of the head. According to ACBA standards, the Crest must be white, with no other white hair present on the animal.
The ANCC (Australian National Cavy Club) recognizes 2 main groups of crested. The American Crested and the English Crested. The American Crested must have a crest colour that is in contrast to the body colour. Usually this is white, but it could be any other colour. These are only recognized in the self colour. English Cresteds have a crest the same colour as the body. These are recognized in every colour and variety, with the exclusion of the "coated" breeds (longhairs and coarse coats). The most popular being breeds such as the English Crested Pink Eyed White and the English Crested Black.

Coronet
A Coronet cavy has longer hair, like the Silkie, along with a crest like a Crested.

English Merino
A curly-coated Coronet with a crest in between the ears on the centre of the head.

Lunkarya
A long-haired breed originating in Scandinavia.

Hairless breeds
A very few varieties of hairless Guinea pig exist, the most prevalent breed being the so-called Skinny pig. Another well-known hairless guinea pig is the Baldwin. Skinny pigs were developed from Teddies and have curly Teddy hair on their noses. Hairless breeds require special accommodation, as they need to be kept warm and require extra food. They also suffer from dry skin, increased incidence of injuries from cagemates, decreased lifespan, and increased incidence of melanoma.
Currently a few Scandinavian bodies admits hairless breeds on to the show table, and consequently a standard of perfection exist.

Ridgeback
Like the Skinny pig and Baldwin, the Ridgeback is not recognized by any international show organization. Genetically, it is similar to an Abyssinian, however, it has few rosettes, and appears to be smooth coated other than a ridge of hair running up the back.

"Abbyruvian"
Abbyruvian is not a recognized breed, but a nickname for Abyssinian cavies that are partially long-haired. Genetically, these animals have one copy of the long-hair allele and one copy of the short-hair allele. Physically, they look like a cross between an Abyssinian and a Peruvian. They generally have short hair on the head, belly, limbs, and rear, and a patch of long hair on the back. The hair typically curls back in such a fashion as to be called a "rooster tail". The same mix of long and short hairs can occur on a smooth-coated cavy, but there is no nickname for it. The long hairs are, however, known as "skirts".

See more details here:
Cavy breeds and coat type

* Agouti coloured cavies have a hair tip and root that are different colours, much like someone whose roots are showing from dyeing their hair. The root contains whatever color from the black series the pig has, and the tip has whichever color from the red series the pig has. Agouti guinea pigs have bellies the same color as the tips of their hair.
o Golden Agouti has a red tip and black root.
o Silver Agouti has a white tip and black (or grayish) root.
o There are also many dilute agouti variations with different combinations of the black series and red series.

* "Solid" coloured cavies are much like Agoutis, but the belly is ticked as well. Solid and Agouti cavies can have patches of solid red series, but all black series hairs wind up ticked.

* "Self" cavies have just one color of hair--black, white, cream, etc.

* Broken colour cavies have two or three colours of hair in any combination not otherwise recognized.

* Tortoiseshell cavies have patches of red and black. For show breeders, the ideal is to have an evenly checkered animal with clear, straight dividing lines between the two colors.
o Tortoiseshell and white cavies have even patches of red, black, and white.

* Brindle cavies have black series and red series hairs evenly mixed throughout their coats. However, these hairs are not ticked.
o Magpie is a particular form of brindle with black for the black series and white for the red series. Magpie can be easily confused with roan, although in magpie the white hairs can appear anywhere, while roan cavies rarely have any white on their head or rear.

* Dutch cavies have bands of color, generally on the cheek area and the rear, with bands of white in-between. The pattern is essentially the same as the Dutch pattern in rabbits.

* Roan and Dalmatian cavies are genetically the same, but look somewhat different. Roans have white hairs evenly mixed throughout their other hairs on back and sides, while Dalmatians have spots of color on a white back and sides. Many are intermediate between the two patterns, with some spots and some mixed-in hairs. The white hairs caused by roan and dalmatian patterns are genetically different from normal white, or the white in the red series, or the white of the Himalayan pattern. Therefore, an animal could have white roan hairs mixed in with white hairs from ordinary white spotting, covering up the telltale roan markings. This is a problem because two guinea pigs who are both roan and/or dalmatian could produce deformed offspring. Hence, no guinea pig with an unknown genetic background and any white hair should be bred.

* Himalayan cavies are acromelanic, just like the Siamese cat. Their noses, ears, and feet are a black series color. If a cavy with Himalayan genes has a genotype that would give them red series, or white, on their nose, ears, or feet, those hairs will be white. This could result in an entirely white animal, or one that is white with black ears, or a half-black nose. Himalayan guinea pigs are always born pure white from the heat of the mother's body, and any colored hairs develop slowly.