This post first appeared on October 22, 2011
As genetic testing has become more common, and there are tests for more and more colors, one thing that has become apparent is that visual identification is not foolproof. Sometimes colors and patterns look alike, but prove to be two different things. The characteristic coloring of the Black Forest Horse is a good example of this.

Many have identified the horse in the picture below as a black silver. He is in fact a chestnut. In his case, there are clues that he is not actually a silver. Although the lighting in the picture makes it less obvious, his coat has red undertones that are more typical of a chestnut than a black-based silver. Even more noticeable is the red coloring at the top of his tail. Visually, it would be possible to guess he is not a silver. There are, however, a lot of Black Forest Horses that don’t give so many clues.

The Black Forest Horse was the subject of a study that determined the stallions currently standing were all genetically chestnut. (Stallions from each of the sire lines can be found here.) Even more interesting, some portion of them carried the rare alternate form of chestnut (e^a) previous only known in the Asturcón and other primitive Iberian breeds. There was no correlation between the alternative chestnut allele and the distinctive flaxen-maned liver of the Black Forest Horses, though. Whatever causes the horses to be so dark, and to have such bright, contrasting manes is not currently known. It would be interesting to find out, because the horses have the same look as black silver without some of the downsides. Reports are that the Black Forest Horses keep their contrasting manes and tails over their lifetimes, a claim that is supported by the appearance of many of the older breeding stallions. Silvers, on the other hand, tend to have manes and tails that darken somewhat with age. Perhaps even more appealing, the coloring on the Black Forests is not linked with Multiple Congenital Ocular Anomalies (MCOA, formly known as ASD), an congenital eye defect thought to be caused by a gene residing close to the silver gene.
Note: The link here has been updated to direct to a genetic survey of MCOA done in 2020.

As more tests are developed, we are likely to find more and more of these look-alike colors and patterns. In the meantime, it is still fun to speculate about what might be found!

(All pictures in this post come from Wikimedia Commons.)