Colour Genetics - Ricinda Ranch

Red Factor
Horses that are chestnut, palomino, red dun, red roan, cremello are red pigmented horses that carry two copies of the Red Factor (e) allele. The red allele is recessive so will only cause a red pigmentation base when the horse carries two of the alleles. To get red pigmentation both parents must pass on the red allele.

Black Factor
Horses that are black, bay buckskin, grulla, perlino,  blue roan etc are black pigmented horses that carry at least one copy of the Black Factor (E) allele.  The black allele is dominant so it causes a black pigmentation base in both the heterozygous (Ee) or homozygous (EE) state. A horse that is heterozygous for red/black base (Ee) carries one of the red and black allele.  A horse that is heterozygous can pass on either the red or black allele to their foal. A homozygous black (EE) horse will always produce a black based foal regardless of its mate

Agouti (Bay/ Black)
The Agouti gene controls the distribution of black pigment. This pigment (A) can either be uniformly distributed or distributed to points on the body (legs, mane tail). The deletion of this gene is the recessive form of this gene (aa).  Only when the agouti gene is homozygous for the deletion is the black evenly distributed. Heterozygous (Aa) or homozygous for the absence of the deletion will have black distributed to the points. The agouti gene has no affect on the red allele as there is no black pigment for the gene affect.

Cream Dilution
The cream dlution (Cr) affects both the red & black pigment & is responsible for diluting the horses colour to a lighter shade.  Horses carrying a single cream  dilution (Cr cr) is called single dilute such as palomino (red based) or buckskin/ smoky black (black based) and these horses has 50% chance on passing the gene to offspring. A horse carrying two copies or homozygous for the cream dilution is called a double dilute and they have 100% chance of passing the cream dilution onto offspring.

Dun Dilution
 
The Dun gene is a dilution gene that affects both red and black coat color pigments. The gene is associated with "primitive marking" and has the ability to affect the appearance of all black, bay, or chestnut ("red")-based horses to some degree by lightening the base body coat.

Silver Dilution

Silver Dilution is a dominant trait, so in order to inherit the trait, a horse requires only one parent to carry and pass on the gene. Somewhat similar to the agouti gene, the silver dilution gene will only alter black pigmented horses (Ee or EE) and has no effect on red pigmented horses (ee). The agouti gene alters the coat by controlling distribution of the black pigment whereas the silver dilution gene does so by diluting areas of black pigment

Roan

Roan horses have white hairs fairly evenly distributed throughout the coat of the main body, with non roaned heads and points (mane, tail, and lower legs). Roaning can give a horse’s coat a silvery effect. Roan horses can be of any color, roaning being a pattern rather than a color itself, but the contrast is more striking on dark colors. Roaning may be "masked" by gray, and can occur in combination with dun, any of the pinto or appaloosa patterns. The roan pattern may not occur until after the first foal coat is shed, but it is then stable throughout life

Champagne Dilution

The Champagne dilution gene lightens a horse's coat color by diluting the pigment. The specific color produced will depend on the horse's base color -- black coats can lighten to a dark brown, chestnut coats to an apricot or gold, and bay coats to a golden brown. A horse can carry more than one dilution gene which can further affect coat color.

Gray

Gray is the dominant gene responsible for the gradual and progressive de-pigmentation (fading) of the carrying horse. Gray cannot be considered a base-color, or a dilution, but rather a gene which slowly removes pigment from the coat. Gray is considered to be the 'strongest' of all coat modifiers, and acts upon any base-color regardless of the carrying horse's phenotype. The fading process itself may last for years, but once hair is de-pigmented, the horse's original coloring will never return.

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