A "red dun" is a coat color found in horses, characterized by a reddish-brown body with a lighter mane and tail. This color can vary in shade, often appearing as a warm, coppery hue. The red dun coat may also have a distinct dorsal stripe running down the back, along with leg barring or other primitive markings. The red dun color is commonly seen in several horse breeds, including the Quarter Horse and Mustang. This coloration is a result of the interaction between specific genes that influence coat color, making it a unique and attractive option for horse enthusiasts.