Base Color Genes:​

These genes control the base color of the horse. 

• Extension: (dominant).

  • E: Controls the amount of black pigment in the hair. EE and Ee horses are black or bay, while ee horses are chestnut.  ​

• Agouti: (dominant).

  • A​: Restricts black pigments to points; causes black horses to become bay. 

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Dilution Genes:

These genes dilute the existing base color of the horse. 

• Dun: (dominant).  

  • D: Horse shows a diluted body color to pinkish-red, yellow-red, yellow or mouse gray and has dark points including dorsal stripe, shoulder stripe and leg barring.

  • D1: Causes counter-shading.These horses are expected to have a dorsal stripe and possibly other markings usually associated with dun. Horses that are positive for d1 but not dun are NOT dun.

• Cream/Pearl Gene: (incomplete dominant).  

  • nCr: Single dilution factor (heterozygous dilute) results in Palomino, Buckskin or Smoky Black. Red pigment is diluted to gold with cream to white mane and tail; black pigment is not visibly altered on black points or black horses, though genetic testing can reveal "smoky black" coloration.​

  • CrCr:  Cremello or Perlino: Double dilution factor (homozygous dilute). Red pigment is diluted to a pale cream. Black pigment is diluted to a reddish shade. Skin and eye color are also diluted, skin is pink and blue eyes are common with double diluted creams.

  • nprl: no effect on its own. 

  • prlprl: Two doses on a chestnut background produce a pale, uniform apricot color of body hair, mane and tail. Skin coloration is also pale.

  • prlCr: Produces pseudo-double Cream dilute phenotypes including pale skin and blue/green eyes.​

• Champagne:  (dominant).

  • Ch: Creates pumpkin-colored freckled skin, amber, greenish, or blue eyes, and gives a bronze cast to hair. The skin surrounding the eye must be pink with freckles in adulthood. 

• Silver Dapple: (dominant).  

  • Z: Dilutes black pigment. Converts black to brown with white mane and tail or results in silver coloring.

• Grey:  (dominant). 

  • G: Horse shows progressive silvering with age to white or flea-bitten, but is born a non-gray color.

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Subjective Dilutions

• Pangare/Mealy: (dominant).  ​

  • P: It lightens the coat of chestnut and bay horses along the flanks, belly, inner legs, at the muzzle and around the eyes.  Does not present on black horses. ​

• Sooty: (dominant). 

  • Sty: Sooty adds black or darker hairs mixed into a horse's coat, typically concentrated along the topline of the horse and less prevalent on the underparts. Does not present on black horses. 

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KIT-Gene​​

• Tobiano:  (dominant). 

  • T: Produces regular and distinct ovals or rounded patterns of white and color with a somewhat vertical orientation. White extends across the back, down the legs, but face and tail are usually dark. ​

• Sabino: (dominant).  

  • Sb: Recognized by abundant white on the legs, belly spots or body spots that are can be flecked and roaned, chin spots, or white on the face extending past the eyes.

• Roan: (dominant).  

  • Rn: Roan pattern of white hair mixed in with base color.

• White: (dominant). Horse has pink skin and white hair, brown or dark eyes. Hair coat is white from birth.​​​ Info from here.

  • WW: Lethal. Embryo reabsorbed or fetus dies en utero.​ Most white alleles are fatal if homozygous. 

  • W20:  Minimal Sabino-like pattern (hetero- und homozygous), increases amount of white with other W variants or other pattern mutations. Most common, and appears in most breeds. 

  • W1, W2, W3, W4, W9, W11, W24: all white. 

  • W5, W10, W27: Sabino-like pattern up to completely white coat

  • W6, W8: Sabino-like full pattern

  • W7, W16, W23: Almost completely white coat

  • W15, W18: Sabino-like pattern

  • W17, W22: White coat, differently colored eyes possible

  • W19: Moderate Sabino-like pattern

  • W25: Sabino-like pattern with great amount of white, colored patches may be diluted/greyish

  • W26: Sabino-like pattern (strongly variable), colored patches may be diluted/greyish

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Other White Marking Genes​

• Overo: dominant.

  • OO: is lethal white syndrome, characterized by an incomplete colon and the inability to defecate, which leads to death or humane euthanization within days of birth.​

  • nO: Pattern that forms a solid frame around white spotting. White is usually horizontal in orientation with jagged edges, color crosses the back and legs, face is often white.

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Appaloosa Complex

• Leopard Appaloosa:  incomplete dominant. Produces coat spotting patterns, mottling over otherwise dark skin, striped hooves and white sclera around the eye.

  • LpLp:

  • nLp: Varnish Roan. Intermixed dark and light hairs with lighter colored area on the forehead, jowls and frontal bones of the face, over the back, loin and hips. Darker areas may appear along the edges of the frontal bones of the face as well and also on the legs, stifle, above the eye, point of the hip and behind the elbow. The dark points over bony areas are called "varnish marks" and distinguish this pattern from a traditional roan.

• PATN1: dominant. 

  • LpLp Patn1Patn1  or LpLp nPatn1: Few Spot. A mostly white horse with a bit of color remaining around the flank, neck and head.​

  • nLp Patn1Patn2: Leopard.  A white horse with dark spots that flow out over the entire body. Considered an extension of a blanket to cover the whole body.​

• PATN2: dominant. 

  • LpLp Patn2Patn2 or LpLp nPatn2: Snowcap. A solid white area normally over, but not limited to, the hip area with a contrasting base color.​

  • nLp Patn2Patn2 or nLp nPatn2: Spotted Blanket. A white blanket which has dark spots within the white. The spots are usually the same color as the horse's base color.

• Combination

  • LpLp nPatn1 nPatn2: Semi-Leopard. Usually combines Snowcap and Leopard. ​