Friesian horses are a beautiful breed. They are almost universally completely black. The red gene can still be found in the population at low frequency. This means that on rare occasions chestnut foals can be born.
Breeders of both pure- and part-bred Friesians also need to make sure they know which of their horses carry the genes for hydrocephalus and Friesian dwarfism.
Gene or region and technical reference
Gene: Various (). Reference: