Today I briefly did a double check on the inheritance of the manchado pattern (a very rare pinto pattern!) and instead came across a blog post from the Equine Tapestry (a great horse color genetics blog I've followed for years) about how seal brown probably isn't an Agouti allele which I'd totally missed.
So anyway now I gotta change the seal brown genetics in my horse breeding tool I guess.
confession: I have not yet decided if I should attempt to simulate KIT and extension linkage in my horse breeding sim tool