We've had this discussion about my black arab mare on many occasions and it appears to be the same situation here.
He looks to be a fading black, as opposed to a true black. A true black always looks jet black regardless of the season (usually with a blue tinge) whereas a fading black changes colour from jet black to what looks like a chocolate brown to a seal grey as the weather warms or cools.
At the moment my mare is identical in colour to your little guy (black looking overall but with red chocolatey hairs top of tail and forelock) but she'll darken out as summer progresses to jet black when she has no fine (warmth) hairs and finally will fade to a seal (like black slate) colour before getting her winter coat again which will then have a red hue to it.
On her registration papers she is listed as black (which is correct) but at the moment she looks chocolatey brown. I'd upload a pic if I knew how.
True 'True Blacks' are quite rare with the majority of 'black' horses actually being fading blacks.
There are heaps of sites on the internet which will verify what I've just said (having been through the whole colour research thing myself - after my mother was ready to sue the breeder for falsely representing her colour etc

) and sorry if my answer's a bit waffly.
Hope that helps
