Terminology
Non-horse people often refer to many horse coat colors as "brown," in particular the bay color. Among horse aficionados, a common assessment is that "... is only used by people with one horse or with two hundred." The implication is that lay observers will refer to a horse's coat color to be "brown" due to a lack of vocabulary, and those discussing large populations of horses will use "brown" out of a need for a more specific vocabulary. The term "seal brown" is unlikely to be part of a novice's repertoire and is therefore preferable when discussing this specific coat color. This coat color is, illuminatingly, called "black and tan" in some languages.
Read more about this topic: Seal Brown (horse)