At first glance the #5907 Appaloosa (2009-11) and #5397 Horse Crazy Gift Collection (2015-Current) models appear identical, but #5907 has stenciled socks and a (usually) matte finish while #5397 has airbrushed socks and a more satin to semi-gloss finish.
#5377 Barrel Racing (2014-Current) is a creamy caramel, shaded buckskin with brown points and no white markings.
K-Mart Special Run #6126 Stablemates Gift Collection (2008) is a lemon yellow buckskin with a near-hind sock and black points.
Passage to the Pacific Special Run #712080 Hear Me Roar (2012) at a stretch could be called a wild bay buckskin. The overall colour is a creamy brown with heavily shaded shoulders and neck, and painted details on the hooves. The intent was to evoke the impression of a lion.
JCPenney #410421 Stablemate Parade of Breeds - Mustang (2007) is a black roan with black points, eye-whites, and warpaint.
JCPenney #410512 Stablemate Parade of Breeds - Mustang (2009) is a bay roan with grey body shading, black mane and tail, brown head and legs, blaze, eye-whites, and near-fore and off-hind socks.
Many thanks to Connie Duncan, and MySt of My Stablemates for providing pictures for this post!