Chestnut/red Friesians are modernly known as Fox Friesians, and they are full-blood Friesians, and CAN, in most cases, be registered as such with the FPS, if the foal has registered parents (though they remain in the Foalbook and cannot be tried for any premium status like Ster et cetera...). However, the practice of selectivly breeding Fox Friesians is not desired or encouraged!
Friesians historically were any coat colour, then for cosmetic purposes, selectively breed for black (w/only a small star of white allowed for registry purposes). Chestnut is a recessive gene, and can show face at any given time, if both parents carry the gene, and is pretty much chance. Obviously, if one horse is homozygous it will never breed anything else but black. You can test horses through a Red Factor test (usually for about 25 to 35 dollars) if you're looking to breed red or black, exclusively.
Stallions are tested for the gene, and nowadays it's taken in consideration for approval purposes, mostly to allow mare owners the choice, esp. If they're mares are tested. Friesians are pretty inbred with a minimum number of stallions available, the gene will never be gone completely, and was traced back to one stallion (whose identity escapes me right now. Uh.
) who was majorly at fault and therefore lost his breeding rights. However, there ARE
FPS approved stallions that are positive for the gene and still breeding...including my gelding's sire, Jillis 301, and one of my faves, Laes 278. 8)
Foxes had a popularity spurt about two years ago. Some brokers of Friesians in Europe even offered a service to importers to help you locate one. Given the fact that it is rare, the horses still cost the same as a black Friesian... and if this had not been the case, the boom would have lasted. But...it didn't.
Personally, I like them! I always dreamed of owning a pair, naming them Tasuki and Schuldig, and tandem driving them!