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# Black dun
- URL: https://equinecolors.com/black-dun/
- Published: 2025-11-24T13:30:30.000Z
- Updated: 2026-08-10T10:41:43.000Z
- Description: Black dun (also called grullo or mouse/blue dun) is a horse color caused by the dun dilution on a black base. The coat is diluted, and primitive markings are present.
- Author: Hannelore Roodhooft
- Tags: Colors, Dilutions, #Import 2026-08-12 09:42

## Appearance

| Foals | ![Black dun foal](https://equinecolors.com/content/images/2025/11/blackdunfoal.png) | Black dun foals have a **mousy grey**coat color and [**primitive markings**](https://equinecolors.com/dictionary/#:~:text=a%20bay%20horse.-,Primitive%20markings,-Primitive%20markings%20may).Foals that also have grey often haveintense primitive markings. |
| ----- | ----------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |

| Dun on a **[black](https://equinecolors.com/black/) base** dilutes the coat to a**blueish grey** color, sometimes with beigetones. The color can vary from light to darker.It also causes **primitive markings**. Points, primitive markings, and (usually) the head are black. | ![Black dun](https://equinecolors.com/content/images/2025/11/blackdun.png) | Adults |
| ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------- | ------ |

### Mimics

![CTA Image](https://equinecolors.com/content/images/2025/12/Equinecolors_Icon_MagnifyingGlass-13.png) 

The ****dun dorsal** stripe goes ****through the tail**, while nd1 dorsal stripes don’t.  
Dun is more likely to cause striping at the ****back of the ears** than nd1.  
****Foals** with dun tend to have a darker ****lower face mask**, while nd1 foals have a darker forehead.

## Genetics

Black dun is the result of a **black base** diluted by **one of two copies of dun**. The dun (D) dilution is an allele of the [**TBX3**](https://equinecolors.com/tbx3-gene/) gene.

![CTA Image](https://equinecolors.com/content/images/2025/12/Equinecolors_Icon_DNA1-36.png) 

****Black dun:**  
Black (E/\_ a/a) + D/\_

Dun is dominant, so horses could carry nd1 or nd2 (located on the same gene) without it being noticeable, but still pass it on. D/nd1 horses possibly tend to be lighter than D/nd2 horses.  

**Read more:**  
[Black](https://equinecolors.com/black/) | [Chestnut dun](https://equinecolors.com/chestnut-dun/) | [Bay dun](https://equinecolors.com/bay-dun/) | [Smoky dun](https://equinecolors.com/smoky-dun/)

[Back to Dun](https://equinecolors.com/dun/)

## Articles

1. An, T.; Dugarjaviin, M.; Han, H. ***Expression and Analysis of TBX3 Gene in the Skin from Three Locations on Dun Mongolian Bider Horse***; Genes (2024); dOI: [0.3390/genes15121589](https://doi.org/10.3390/genes15121589?urlappend=%3Futm%5Fsource%3Dresearchgate.net%26utm%5Fmedium%3Darticle&ref=equinecolors.com)
2. Cieslak J, Brooks SA, Wodas L, Mantaj W, Borowska A, Sliwowska JH, Ziarniak K, Mackowski M.; ***Genetic Background of the Polish Primitive Horse (Konik) Coat Color Variation-New Insight into Dun Dilution Phenotypic Effect***; Journal of Heredity Hered. (2021); Doi: [10.1093/jhered/esab034](https://academic.oup.com/jhered/article/112/5/436/6357767?login=false&ref=equinecolors.com)
3. Imsland, F., McGowan, K., Rubin, C. J., Henegar, C., Sundstrom, E., Berglund, J., Schwochow, D., Gustafson, U., Imsland, P., Lindblad-Toh, K., Lindgren, G., Mikko, S., Millon, L., Wade, C., Schubert, M., Orlando, L., Penedo, M. C., Barsh, G. S., & Andersson, L.; **Regulatory mutations in TBX3 disrupt asymmetric hair pigmentation that underlies Dun camouflage color in horses**; Nature Genetics (2015)*;* Doi: [10.1038/ng.3475](https://doi.org/10.1038/ng.3475?ref=equinecolors.com)
4. Masuda M. Tsunoda J., Nomura H., Kimura N., Altangerel G., Namkhai B., Dolj U., Yokohama Y.***; New Primitive Marking (Bider) in Mongolian Native Horse and Equus przewalskii;*** Journal of Equine Science (2007); Doi: [10.1294/jes.18.145](https://doi.org/10.1294/jes.18.145?ref=equinecolors.com)

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