Bay with gulastra plume:

Gulastra plume, also known as silver tail, is when a horse’s tail is a light flaxen/silver colour when there are no known genes present to turn the tail pale (i.e. silver). It's rare but when found, it is best seen on younger horses, and will often darken with age. It has a large range of expression from bold paleness to only a slight paleness. It is named after the Arabian stallion Gulastra who sired many gulastra plume foals though he himself was chestnut and his tail was not pale.