The differences between these three black Friesians are very subtle and may or may not be consistent throughout the runs.
Stablemate Assortment #5906 Friesian - Black (2006-08) is a faded black with a very dark brown body and black points. The body colour has yellow-toned highlights, the hooves are tan, and the eyes are black with eye-whites.
Multiple Retailers special run Horse-A-Day Calendar (2010-11) is a faded black with a very dark brown body and black points. The body colour has yellow-toned highlights, the hooves are tan, and the eyes are black with eye-whites. Based on the dates one would assume this model is a repackaged #5906, but it is identical to my #5906.
On the bottom row, Stablemate Assortment #5907 Friesian (2009-11) is a faded black with a very dark brown body and black points. The body colour has grey-toned highlights, the hooves are grey, and the eyes are black with eye-whites.
#6022 Gentle Giants (2015-current) is the first true black G3 Friesian. This model is a uniform coal black with eye-whites.
Target special run #720597 Red Stable Set (2006) is a chestnut splash white with apron face, four stockings, pale hooves, and slightly lighter mane and tail.
It has also been released in #59197 Red Stable Set (2007-current) and Big Lots special run #9979197 Stablemates Country Stable Set (2010).
JCPenney special run #410176 Stablemates Parade of Breeds - Welsh Cob (2006) is a light dapple grey with shaded white mane and tail, four socks, light hooves, and misty resist dapples.
K-Mart special run #6126 Stablemates Gift Collection (2008) is a darker, grey shaded dapple grey with bright white mane and tail, off-hind sock with light hoof, dark hooves on the dark legs, and eye-whites.
#5976 Gift Collection (2009-11) is a soft, marshmallow white with light grey shading, four socks, grey hooves and eye-whites.
BreyerFest Breyer Store Special #711080 Stablemates 20th Anniversary Commemorative Set - 2005 Fire Magic (2009) is actually a dark chestnut, but could pass as a wild bay. It is a shaded medium brown with darker mane, tail, and leg joints, and eye-whites.
#5412 Stablemates Horse Lover's Collection Shadow Box - Carriage Horse (2011-16) is a shaded, cherry red bay with black points and a large star.
JCPenney special run #410512 Stablemate Parade of Breeds - Cob (2009) is a medium, minimally shaded bay with near-hind sock, black points, blaze, and eye-whites.
Many thanks to MySt of My Stablemates for providing pictures for this post!