chestnut_thoroughbred_(kemono_friends)
A Kemono Friends character. One of many "Friends" in Japari Park. The Thoroughbred Trio were created for a promotion involving the Anime and the Japan Racing Association. They have since integrated with the wider franchise and the JRA moved on with a different franchise.
Horses and Thoroughbreds are better explained in Brown Thoroughbred (Kemono Friends)'s page.
A "chestnut" horse denotes a horse with a reddish-brown coat and mane without any black hair at the limbs. There are variants such as flaxen chestnut (chestnuts with manes and tails better described as blonde or a lighter red) and liver chestnut (chestnuts with a particularly dark coat). Flaxen liver chestnuts are simply a combination of the two.
Chestnut Thoroughbred is (naturally) a horse girl with long brown hair resembling a mane in a ponytail with a white stripe on the bangs (a "blaze" marking), wearing a brown sports ensemble.