Lets me think of what I'm seeing, without reading the title. What intrigued me the most and first, is the red reflection in the eye. (Reflection of the hair..) It's a very expressive picture, my opinion. Strong..and sad at the same time. Maybe the red and black/white contrasts. Stressed hair and the head in totally rest as in peaceful way. Intriguing picture. Nice, well done.
Now, I don't know about this specific horse, and I'm answering more or less from research. There are two different types of "black" horse - Fading and non-fading.
Non-fading, or "true" black doesn't tend sun bleach in the summer. Fading black often does - the sunlight lightens the mane/tail/sometimes the body hair to some extent, much like some people's hair gets lighter in the summer and darker in the winter, the same principal applies to fading black horses.
The other option is that he's a mix, or that he's a throwback. Registered Fresians must be black as far as I know, but, I don't think they make a distinction for fading/non-fading.
"The official breed rarely has white markings of any kind; most registries allow only a small star on the forehead for purebred registration. Though extremely rare, and not accepted for registration in most cases, Friesians are occasionally chestnut. If a Friesian is chestnut in color and competes, they are penalized, with stallions being more severely penalized. Any discoloration from old injuries or fading from the sun are not counted towards penalties" ^ From the Friesian horse page on Wikipedia (I know, not the most reliable of sources, but it's a place to start, if you'd like to know more?)