Horse Color Calculator — Coat Color Genetics Predictor
Predict horse coat color from genotype: base color, cream, dun, champagne, silver, grey, roan, and spotting patterns, with the Frame Overo lethal warning.
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Full bio →Build a genotype gene-by-gene to predict the resulting coat color and pattern, based on horse coat color genetics documented by UC Davis Veterinary Genetics Laboratory. Start with the base color genes, then add any dilution, whitening, or spotting genes present.
Base Color Genes
This is an educational genotype-to-phenotype model based on published equine coat color genetics (base color: Extension/Agouti; dilutions: Cream, Dun, Champagne, Silver; whitening: Grey, Roan; spotting: Tobiano, Frame Overo, Appaloosa/Leopard complex). Some real-world interactions — especially compound dilutions and the exact expressivity of nd1/nd2 dun alleles — vary more than a simplified model can capture. For an actual animal, especially before a breeding decision, a DNA coat color panel from UC Davis Veterinary Genetics Laboratory is the authoritative source, not this calculator.
Reference Values
Last verified:| Category | Range | What It Means | Status |
|---|---|---|---|
| Chestnut (ee, any Agouti) | Extension: e/e — Agouti: any | No black pigment (eumelanin) possible — the coat and points are entirely red-based pigment (pheomelanin). Agouti genotype is irrelevant once e/e is present. | Good |
| Black (E_ aa) | Extension: E/E or E/e — Agouti: a/a | Black pigment expressed across the entire body with no Agouti restriction — solid black coat, mane, tail, and legs. | Good |
| Bay (E_ A_) | Extension: E/E or E/e — Agouti: A/A or A/a | Agouti restricts black pigment to the "points" (mane, tail, lower legs, ear edges) while the body shows a reddish-brown base — the most common horse color worldwide. | Good |
| Palomino (Chestnut + Cr/n) | Base: Chestnut — Cream: single copy | One copy of cream dilutes the chestnut body to a golden-yellow coat with a flaxen or white mane and tail. | Good |
| Cremello (Chestnut + Cr/Cr) | Base: Chestnut — Cream: double copy | Two copies of cream fully dilute chestnut to a near-white cream coat with blue eyes and pink skin. | Good |
| Buckskin (Bay + Cr/n) | Base: Bay — Cream: single copy | One copy of cream dilutes the bay body to a golden tan coat while the black points (mane, tail, legs) stay dark — cream dilutes red pigment strongly but black pigment only mildly. | Good |
| Perlino (Bay + Cr/Cr) | Base: Bay — Cream: double copy | Two copies of cream dilute bay to a near-white body with a slightly darker (reddish/cream) mane and tail, blue eyes, and pink skin. | Good |
| Smoky Black (Black + Cr/n) | Base: Black — Cream: single copy | One copy of cream has only a subtle lightening effect on black since there is no red pigment for it to strongly dilute — often visually indistinguishable from a plain black without DNA testing. | Good |
| Smoky Cream (Black + Cr/Cr) | Base: Black — Cream: double copy | Two copies of cream dilute black to a cream-colored coat, generally slightly darker/more cream-toned than cremello or perlino, with blue eyes and pink skin. | Good |
| Dun — full dilution (D) | Dominant allele | Dilutes the body coat while sparing the mane, tail, legs, and head, and adds primitive markings: a dorsal stripe, horizontal leg barring, and sometimes a shoulder stripe. Combined with base color: Red Dun (chestnut), Bay Dun / Classic Dun (bay), Grullo/Grulla (black). | Good |
| Dun — nd1 allele | Intermediate allele | Slight body dilution with darker, more distinct primitive markings than nd2 — often subtle enough to miss without a DNA test. | Good |
| Dun — nd2 allele | Weak allele | Minimal to no visible body dilution, but faint primitive markings (dorsal stripe) may still show. This is the most common "non-dun" allele horses actually carry. | Okay |
| Champagne | Dominant, single copy sufficient | Dilutes both red and black pigment evenly (unlike cream's uneven effect), producing Gold Champagne (chestnut base), Amber Champagne (bay base), or Classic Champagne (black base). Foals are born with blue eyes that darken with age and pink skin that develops freckling. | Good |
| Silver | Dominant, acts only on black pigment | Lightens the mane and tail (often to flaxen or silvery-white) and adds dappling to the body on a black or bay base. Has no visible effect on chestnut, which has no black pigment for silver to act on. | Good |
| Grey | Dominant, progressive with age | The horse is born its base color but progressively depigments toward grey and eventually white/flea-bitten grey with age, regardless of starting base color or other modifiers. Skin stays dark underneath — the clearest way to tell true grey from other whitening patterns. | Good |
| Roan | Dominant, static (does not progress with age) | White hairs are intermixed evenly through the body coat while the head and lower legs stay solid-colored. Named by base: Red/Strawberry Roan (chestnut), Bay Roan (bay), Blue Roan (black). Unlike grey, roaning does not spread further once the adult coat is set. | Good |
| Tobiano | Dominant (KIT locus) | Rounded/oval white patches with clean edges, typically crossing the topline (back), with white legs common. One copy is enough to show the pattern. | Good |
| Frame Overo — heterozygous (O/n) | Dominant, one copy | Irregular, horizontal, jagged-edged white patches that rarely cross the back, often with a dark tail and legs. Caused by an EDNRB gene mutation. | Good |
| Frame Overo — homozygous (O/O) — LETHAL | Two copies — Overo Lethal White Syndrome (OLWS) | Foals with two copies of the Frame Overo gene are born mostly or entirely white and lack a properly developed intestinal nerve network (intestinal aganglionosis). They cannot pass waste and die within about 48-72 hours of birth even with veterinary intervention. Two known Frame Overo carriers should never be intentionally bred together without DNA testing both parents first. | Poor |
| Appaloosa/Leopard complex — LP/n (heterozygous) | Dominant, one copy | Leopard or blanket spotting over the hips/body, mottled skin around the eyes/muzzle/genitals, striped hooves, and visible white sclera — the classic Appaloosa look. | Good |
| Appaloosa/Leopard complex — LP/LP (homozygous) | Two copies | Typically produces a fewspot or snowcap pattern — near-total white or very sparse residual spotting — while still showing the mottled skin, striped hooves, and white sclera markers of the LP gene. | Okay |
Source: UC Davis Veterinary Genetics Laboratory (vgl.ucdavis.edu/resources/horse-coat-color); Wikipedia "Equine coat color genetics"; American Paint Horse Association Genetics 101.
Worked Examples
Chestnut + Single Cream = Palomino
- Base Genotype
- e/e (chestnut base)
- Cream (Cr)
- Cr/n (single copy)
One copy of cream dilutes chestnut's red pigment to a golden-yellow body with a flaxen or white mane and tail. Two copies of the same base would instead produce cremello (near-white).
Bay + Double Cream = Perlino
- Base Genotype
- E_ A_ (bay base)
- Cream (Cr)
- Cr/Cr (double copy)
Two copies of cream fully dilute both the bay body and its black points, leaving a near-white coat with a slightly darker reddish/cream mane and tail, blue eyes, and pink skin. One copy on the same bay base would instead produce buckskin.
Black + Silver = Silver Dapple
- Base Genotype
- E_ aa (black base)
- Silver (Z)
- Z/n (present)
Silver acts only on black pigment, so a black-based horse shows the full effect: the mane and tail lighten toward flaxen/silvery-white and the body develops dappling. The same gene on a chestnut base would have no visible effect at all.
Bay + Full Dun = Bay Dun (Classic Dun)
- Base Genotype
- E_ A_ (bay base)
- Dun (D locus)
- D — full dun
Full dun dilutes the bay body coat while sparing the mane, tail, legs, and head, and adds primitive markings — a dorsal stripe, horizontal leg barring, and sometimes a faint shoulder stripe. The same dun allele on a black base produces grullo/grulla instead.
Frame Overo x Frame Overo — Lethal White Warning
- Spotting Pattern
- Homozygous Frame Overo (O/O)
Breeding two Frame Overo carriers together gives each foal a 25% chance of inheriting two copies (O/O). These foals are born mostly or entirely white with an underdeveloped intestinal nerve network and die within 48-72 hours of birth. UC Davis VGL offers a DNA test to confirm carrier status before breeding — never pair two known or suspected Frame Overo carriers without testing both parents first.
How to Use This Calculator
- 1
Set the base color genes
Choose the Extension (E locus) genotype first. If you select e/e, the horse is chestnut and the Agouti selector is disabled since it has no visible effect. Otherwise, choose Agouti to determine bay (A_) versus black (aa).
- 2
Add dilution genes if present
Select cream dosage (none, single, or double copy), a dun level (non-dun, nd2, nd1, or full dun), and whether champagne is present. Each dilution changes the predicted phenotype name and is explained in the results.
- 3
Add whitening and roaning genes if present
Silver only visibly affects black or bay-based horses. Grey causes progressive whitening with age regardless of base color. Roan intermixes white hairs through the body coat without affecting the head or legs.
- 4
Select a spotting pattern if present
Choose tobiano, frame overo (heterozygous or homozygous), or the Appaloosa/leopard complex (single or double copy). Selecting homozygous frame overo (O/O) triggers a prominent lethal white warning.
- 5
Read the predicted phenotype and modifier notes
The result card shows the base color and final predicted coat description, with a bullet list explaining how each selected gene changed the outcome.
What Each Value Means
- Extension (E Locus) (alleles: E, e)
- Controls whether a horse can produce black pigment (eumelanin) at all. e/e means no black pigment is possible, producing chestnut regardless of any other gene. At least one E allele allows black pigment to be produced, subject to Agouti's restriction.
- Agouti (A Locus) (alleles: A, a)
- On a black-pigment-capable horse (at least one E allele), Agouti determines whether black pigment is restricted to the points (mane, tail, legs, ear edges) — producing bay — or expressed across the whole body — producing black.
- Cream Dilution (Cr Locus) (alleles: Cr, n)
- A dose-dependent dilution gene. One copy (Cr/n) produces palomino (from chestnut), buckskin (from bay), or smoky black (from black). Two copies (Cr/Cr) produce cremello, perlino, or smoky cream respectively.
- Dun (D Locus) (alleles: D, nd1, nd2, non-dun)
- A graded dominant dilution: full dun (D) dilutes the body while sparing the mane, tail, legs, and head, and adds primitive markings like a dorsal stripe. The nd1 and nd2 alleles produce progressively fainter versions of the same effect.