Barnrat, if I was going to give more heartfelt advice or insight, I would do more homework than just a quick search if I wasn't already 100% sure of what I was talking about ;) Friesians aren't my dish, and the only things I knew about the breed is that they were war horses, got refined over the years, and were black and hairy ;)
Wikipedia is by far not a perfect source of reference, but it is extremely convenient.. it was just a quickie search for me to use to check some information right quick, since I too was surprised to see a chestnut friesian ;) I had to go feed the herd about 5 minutes after I saw this post, so I didnt have time to do my proper "homework".
The thing that gets me, is she knew the parents of that horse, and they were both black, very ordinary friesians. Heck, if I saw it myself I would have a hard time believing it!
And honestly, it really doesn't bother me if you "start believing" me or not.. Im not here to prove a point, or be a know it all, or sound important or smart. I enjoy participating in the conversations, and adding a word in edgewise when I can ;) I don't claim to be an expert on Friesians, so honestly, my word -really- doesn't count anyways ;).
**ETA** Did more homework on Chestnut Friesians:
Of course the color is (almost) always black with no white markings, all though a tiny star is permissible – usually only a few hairs.
These horses were larger & stockier than the Friesian of today, and could originally be found in a variety of colors from grey to bay to chestnut. Over centuries they were selectively bred to produce only black. Occasionally still, an odd chestnut Friesian foal will be born.
Since Chestnut is recessive it can be "hidden", for many generations, thus it may seem to pop up out of nowhere at times. This is how the beautiful Chestnut Friesian mare (left) came about. Research several generations back may be required to find out exactly where this recessive gene came into play.
Source (with photo!): http://www.equinecolor.com/chestnut.html
Blood-typing proved that Obizuth is indeed a purebred Friesian, despite her unorthodox hair color. The FHANA registry finally decided that she could be registered in the foal book registry but that her offspring would be unregisterable. This means that desite being one of the few chesnut Friesians (last count a grand total of 4) in the world, her monetary value is slight. That's all right, she NOT for sale anyway.
Source (with photos!): http://www.geocities.com/Heartland/4075/obizuth.html
Are they always black?
They are now, but up-to a 100 hundred years ago, there were white, roan and chestnut Friesians horses. White is now not acceptable except for a small star on the forehead. The ideal horse is jetblack, but very dark black and rusty black is acceptable. A Friesian can become brown if they are sun or sweat bleached. On very rare occasions, a chestnut foal is born.