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Methods and sources

How the horse coat color tools work

The horse coat color calculator and visualizer turn published equine color genetics into illustrated results. This page explains the method, what the tools cover and leave out, and the research behind them, so you can judge every result for yourself.

Reviewed by Elliott Garber, DVM · Last reviewed

What the tools do

The calculator shows the coat colors a foal could inherit from two parents. You can start from the colors you see on each parent, or from their DNA results.

The visualizer shows one horse. Enter the DNA results you know and it illustrates the coat color and patterns they produce, with notes on what each gene does.

How foal odds are calculated

Each parent passes one copy of each gene to a foal, chosen at random. Genes on different chromosomes are inherited independently. From DNA results, the calculator multiplies these chances out exactly.

From coat colors alone, one color can come from several genotypes: a bay might carry red (e) or not. The calculator lists every genotype that fits each parent’s color and works out the foal odds for each combination. When every combination gives the same answer, you see one exact percentage. When they differ, you see the range: at least the smallest chance and up to the largest.

We never average a range, take its midpoint or fill gaps with breed or population frequencies. Those numbers would look precise while hiding what nobody knows about these two horses. A DNA test is what narrows a range, and the calculator suggests which test would help most.

Silver, Pearl and Cream can hide in a coat: Silver on a chestnut, a single copy of Pearl, or Cream on a black coat. The full ranges always include those hidden possibilities, which is why the full range for a black foal from two black parents is 18.75% to 100% rather than 75% to 100%: a black coat could be hiding Cream or Pearl. When the foal color map leads with chances that assume neither parent hides Silver, Pearl or Cream, it says so right under the map, and the full ranges stay one click away.

Every percentage is per conception. Combinations that cannot survive, such as Lethal White Overo from two Frame Overo carriers, stay in the total and are named, so the chance of a living foal of any color is never overstated.

Genes that travel together

Two separate regions of chromosome 3 matter for coat color. One, toward the end of the chromosome, holds Extension and PATN1. The other is the tightly packed KIT region, home to Tobiano, Roan, Sabino 1 and the Dominant White variants. The tools handle the two regions separately.

Within a region, when a lab report shows which variants sit together on each chromosome, the tools use that arrangement. When it does not, or when published research gives no reliable rate of crossing over, the tools show each possible arrangement separately and do not weight one over another.

Brindle1 is on the X chromosome, so a colt inherits it only from his dam. That is why the visualizer asks for the horse’s sex.

What the tools do not model

  • Shade modifiers such as sooty, flaxen, pangaré (mealy) and dapples. Their genetics is not settled enough to predict.
  • Face and leg white markings, which are influenced by many genes.
  • Rabicano, birdcatcher spots and other roaning or ticking not caused by the tested Roan variant.
  • KIT, MITF and PAX3 variants that common test panels do not report. New variants are still being found.
  • How large a white or leopard pattern will be. Pattern size varies between horses with the same genotype, so the pictures show a typical range.
  • The age at which a gray horse lightens. Gray stages are illustrations, not a timeline.
  • Breed-specific frequencies. These are left out on purpose, as explained above.

Health notes

Some color genes also affect health. The tools flag these whenever a result involves them. The notes summarize published research and are not a diagnosis: ask your veterinarian what a result means for a particular horse.

  • Lethal White Overo: foals with two Frame Overo (O/O) copies are born white with an intestinal defect and do not survive (EDNRB).
  • Multiple Congenital Ocular Anomalies: eye changes associated with the Silver variant in PMEL, more extensive with two copies.
  • Congenital stationary night blindness: associated with two copies of Leopard Complex (LP/LP), in TRPM1.
  • Gray: gray horses are at higher risk of melanoma as they age (STX17).
  • Some Splashed White variants are associated with deafness, and some Dominant White variants are thought to be lethal before birth in two copies.

Limitations

  • Results are only as accurate as the colors or lab results entered. Labs name some tests differently; the forms use the names on common VGL and APHA panels.
  • The illustrations show a typical horse for each result. Real horses vary in shade, markings and pattern.
  • From coat colors alone, a range is the honest answer. Testing the parents is the way to narrow it.
  • These are educational tools. They do not replace a laboratory report or veterinary advice for breeding or health decisions.

Genes and tests covered

Both tools use the color tests on common horse panels. Each row links to the UC Davis Veterinary Genetics Laboratory test page and the research that identified the variant.

TraitGeneChromosomeResultsWhat it doesSources
Red or black (Extension) MC1R 3 E, e, ea E allows black pigment; two red alleles (e or ea) give a chestnut base. Lab test [1] [2]
Agouti ASIP 22 A, a A keeps black to the mane, tail and legs (bay); a/a leaves black everywhere. Lab test [2]
Cream and Pearl SLC45A2 21 N, Cr, Prl One Cream lightens red (palomino, buckskin); two lighten black too (cremello, perlino). Pearl shows with two copies or with one Cream. Lab test [3] [4]
Champagne SLC36A1 14 N, Ch Lightens red and black, with freckled pink skin and amber eyes. Lab test [5]
Dun TBX3 8 D, nd1, nd2 D lightens the body and adds a dorsal stripe and leg barring; nd1 gives faint markings without lightening. Lab test [6]
Silver PMEL 6 N, Z Lightens black pigment, most in the mane and tail. Not visible on chestnut. Lab test [7] [8]
Gray STX17 25 N, G (G2, G3 copy number) The coat whitens with age, on any base color. Lab test [9]
Mushroom MFSD12 N, Mu Two copies lighten red to a sepia mushroom shade. Lab test [10]
Frame Overo EDNRB 17 N, O One copy can give frame overo white (sometimes very little); two copies cause Lethal White Overo. Lab test [11] [12]
Tobiano near KIT 3 To White patches that usually cross the back, with white legs. Lab test [13]
Roan KIT (linked marker) 3 Rn White hairs through the body coat; head and legs stay darker. Lab test [14]
Sabino 1 KIT 3 SB1 White legs, face and belly with roaned edges; two copies are often mostly white. Lab test [15]
Dominant White KIT 3 W4, W5, W10, W13, W20, W22 and others From extra white markings to an all-white coat, depending on the variant. Lab test [16]
Leopard Complex and PATN1 TRPM1, RFWD3 1, 3 LP; PATN1 LP gives appaloosa spotting; PATN1 adds extensive white such as a leopard or blanket. Lab test [17] [18]
Splashed White MITF, PAX3 16, 6 SW1, SW2, SW3 and other variants White legs, belly and blaze, as if dipped in white paint. Lab test [19]
Brindle1 MBTPS2 X BR1 X linked. Mares with one copy show vertical brindle stripes and coat texture; mares with two copies and males with one show a sparse mane and tail without the stripes. Lab test [20]

References

  1. Marklund L, Moller MJ, Sandberg K, Andersson L. A missense mutation in the gene for melanocyte-stimulating hormone receptor (MC1R) is associated with the chestnut coat color in horses. Mammalian Genome. 1996;7:895-899. doi:10.1007/s003359900264
  2. Rieder S, Taourit S, Mariat D, Langlois B, Guérin G. Mutations in the agouti (ASIP), the extension (MC1R), and the brown (TYRP1) loci and their association to coat color phenotypes in horses. Mammalian Genome. 2001;12:450-455. doi:10.1007/s003350020017
  3. Mariat D, Taourit S, Guérin G. A mutation in the MATP gene causes the cream coat colour in the horse. Genetics Selection Evolution. 2003;35:119-133. doi:10.1186/1297-9686-35-1-119
  4. Holl HM, Pflug KM, Yates KM, et al. A candidate gene approach identifies variants in SLC45A2 that explain dilute phenotypes, pearl and sunshine, in compound heterozygote horses. Animal Genetics. 2019;50:271-274. doi:10.1111/age.12790
  5. Cook D, Brooks S, Bellone R, Bailey E. Missense mutation in exon 2 of SLC36A1 responsible for champagne dilution in horses. PLoS Genetics. 2008;4:e1000195. doi:10.1371/journal.pgen.1000195
  6. Imsland F, McGowan K, Rubin CJ, et al. Regulatory mutations in TBX3 disrupt asymmetric hair pigmentation that underlies Dun camouflage color in horses. Nature Genetics. 2016;48:152-158. doi:10.1038/ng.3475
  7. Brunberg E, Andersson L, Cothran G, Sandberg K, Mikko S, Lindgren G. A missense mutation in PMEL17 is associated with the Silver coat color in the horse. BMC Genetics. 2006;7:46. doi:10.1186/1471-2156-7-46
  8. Andersson LS, Wilbe M, Viluma A, et al. Equine Multiple Congenital Ocular Anomalies and Silver coat colour result from the pleiotropic effects of mutant PMEL. PLoS ONE. 2013;8:e75639. doi:10.1371/journal.pone.0075639
  9. Rosengren Pielberg G, Golovko A, Sundström E, et al. A cis-acting regulatory mutation causes premature hair graying and susceptibility to melanoma in the horse. Nature Genetics. 2008;40:1004-1009. doi:10.1038/ng.185
  10. Tanaka J, Leeb T, Rushton J, et al. Frameshift variant in MFSD12 explains the mushroom coat color dilution in Shetland ponies. Genes. 2019;10:826. doi:10.3390/genes10100826
  11. Santschi EM, Purdy AK, Valberg SJ, Vrotsos PD, Kaese H, Mickelson JR. Endothelin receptor B polymorphism associated with lethal white foal syndrome in horses. Mammalian Genome. 1998;9:306-309. doi:10.1007/s003359900754
  12. Metallinos DL, Bowling AT, Rine J. A missense mutation in the endothelin-B receptor gene is associated with Lethal White Foal Syndrome: an equine version of Hirschsprung disease. Mammalian Genome. 1998;9:426-431. doi:10.1007/s003359900790
  13. Brooks SA, Lear TL, Adelson DL, Bailey E. A chromosome inversion near the KIT gene and the Tobiano spotting pattern in horses. Cytogenetic and Genome Research. 2007;119:225-230. doi:10.1159/000112065
  14. Marklund S, Moller M, Sandberg K, Andersson L. Close association between sequence polymorphism in the KIT gene and the roan coat color in horses. Mammalian Genome. 1999;10:283-288. doi:10.1007/s003359900987
  15. Brooks SA, Bailey E. Exon skipping in the KIT gene causes a Sabino spotting pattern in horses. Mammalian Genome. 2005;16:893-902. doi:10.1007/s00335-005-2472-y
  16. Haase B, Brooks SA, Schlumbaum A, et al. Allelic heterogeneity at the equine KIT locus in dominant white (W) horses. PLoS Genetics. 2007;3:e195. doi:10.1371/journal.pgen.0030195
  17. Bellone RR, Holl H, Setaluri V, et al. Evidence for a retroviral insertion in TRPM1 as the cause of congenital stationary night blindness and leopard complex spotting in the horse. PLoS ONE. 2013;8:e78280. doi:10.1371/journal.pone.0078280
  18. Holl HM, Brooks SA, Archer S, et al. Variant in the RFWD3 gene associated with PATN1, a modifier of leopard complex spotting. Animal Genetics. 2016;47:91-101. doi:10.1111/age.12375
  19. Hauswirth R, Haase B, Blatter M, et al. Mutations in MITF and PAX3 cause "splashed white" and other white spotting phenotypes in horses. PLoS Genetics. 2012;8:e1002653. doi:10.1371/journal.pgen.1002653
  20. Murgiano L, Waluk DP, Towers R, et al. An intronic MBTPS2 variant results in a splicing defect in horses with brindle coat texture. G3: Genes, Genomes, Genetics. 2016;6:2963-2970. doi:10.1534/g3.116.032433
  21. Andersson LS, Axelsson J, Dubielzig RR, Lindgren G, Ekesten B. Multiple congenital ocular anomalies in Icelandic horses. BMC Veterinary Research. 2011;7:21. doi:10.1186/1746-6148-7-21
  22. Sponenberg DP, Bellone RR. Equine Color Genetics. 4th ed. Wiley-Blackwell; 2017.
  23. UC Davis Veterinary Genetics Laboratory. Horse coat color tests and reference. https://vgl.ucdavis.edu/resources/horse-coat-color

How to cite or link to these tools

You are welcome to link to the calculator, the visualizer or this page from teaching materials, extension articles and client handouts. Suggested citation:

Creatures. Horse Coat Color Calculator and Visualizer: methods and sources. https://creatures.com/horse-coat-color-calculator/how-it-works. Reviewed by Elliott Garber, DVM; last reviewed October 20, 2026.

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Changes

  • : Methods, sources and reviewer published; foal color map shows exact odds or honest ranges for every color.